William J. O'Neil
CAN SLIM: seven conditions, and the one that can veto the other six
William O'Neil studied the biggest stock winners of the previous century and asked what they had in common before they ran. The answer became seven letters. Six of them describe the company; the seventh describes the weather, and it has a veto over the other six — which is the part of CAN SLIM that most summaries leave out.
- Style
- Momentum
- Approach
- Discretionary
- Difficulty
- Advanced
- Horizon
- Position (weeks to months)
- Holding period
- Weeks to months
- Time needed
- 2-3 hours a week screening and tracking earnings
- Markets
- US equities · Growth stocks
- Source
- How to Make Money in Stocks (4th edition, McGraw-Hill) — William J. O'Neil
The rule set
- C — Current quarterly earnings per share up sharply against the same quarter a year ago; O'Neil's floor was 25%
- A — Annual earnings growing consistently over the last three to five years, not one good year
- N — Something new: a product, a management, an industry condition — and a price making a new high out of a base
- S — Supply and demand: a manageable share count, and volume expanding on the up-days
- L — Leader, not laggard: buy the strongest name in a strong group, measured by relative strength
- I — Institutional sponsorship increasing, but not yet universal — you want funds buying, not finished buying
- M — Market direction: only buy while the general market is in a confirmed uptrend. This one overrides the rest
- Risk: sell any position that falls 7–8% below your purchase price, with no exceptions and no averaging down
What makes it distinctive
- Seven conditions you can literally tick off, derived from a study of what past big winners looked like before they moved
- Requires fundamental and technical confirmation together, which filters out both story stocks and chart patterns with nothing behind them
- Comes with hard loss discipline attached — out at 7–8% below the pivot, without exception, which is the rule that makes the rest survivable
When it works
Growth-led bull phases where a new industry or technology throws up a handful of leaders with genuinely accelerating earnings, and institutions accumulate them over months.
When it fails
In bear markets and value-led rotations almost nothing passes the screen, and the M rule correctly keeps you out. When high-growth multiples compress, the 7–8% stop triggers over and over — a sequence of small losses that is individually correct and collectively demoralising.
How a decision moves through it
Input
Quarterly and annual earnings, share count, ownership, price and volume
The only system here that needs a fundamental data feed as well as a price one. That is a real operational cost and it is why the screen runs weekly rather than daily.
Decide
C, A, N, S, L, I — the company screen
Six independent tests. O'Neil's guidance is that a candidate should pass all of them, not average well across them — a weak L is not offset by an excellent C.
Decide
M — is the general market in a confirmed uptrend?
Evaluated separately, before any individual name. A no here means no purchases at all, regardless of how many candidates the screen returned.
Measure
The base and its pivot
A cup-with-handle or similar consolidation, with a specific buy point at the top of the handle. The pivot is a price, not a zone, and everything downstream measures from it.
Act
Buy at the pivot, on volume
Volume on the breakout day should be far above average — O'Neil looked for 40–50% above normal. A quiet pivot break is a failure candidate.
Size & protect
Cut at 7–8% below the pivot
A maximum, not a target. It is tied to the pivot entry: buy late, above the pivot, and the same percentage stop is no longer measuring the same thing.
It is a description of past winners, not a theory
O'Neil's method was built backwards. He took the stocks that produced the largest gains in each market cycle, went back to the point just before each one advanced, and catalogued what they had in common. CAN SLIM is that list of common features, turned into a screen.
That origin is both its strength and its main methodological weakness. It describes what big winners looked like beforehand — it does not tell you how many stocks looked identical and went nowhere.
This is survivorship in the structure of the method itself, and it is worth naming plainly. The screen is a necessary-condition filter, not a sufficient one. Passing all seven letters does not make a stock a winner; failing them made a stock very unlikely to have been one of O'Neil's winners.
M is not the seventh criterion — it is a gate in front of the other six
O'Neil's own estimate, repeated throughout his writing, is that roughly three out of four stocks follow the general market's direction. A perfect CAN SLIM candidate bought during a market correction is a stock with excellent fundamentals falling with everything else.
So M is evaluated first and separately. It is not a tiebreaker between candidates; it decides whether you are buying anything at all this week. In practice this means the system produces long stretches with a full watchlist and zero purchases.
Why neither half of the system works alone
Fundamentals alone
- A company can grow earnings 40% for two years while the stock does nothing
- No entry point, so position sizing has nothing to anchor to
- No exit — 'still a great company' is not a sell rule
- You are early, potentially for years
Chart alone
- Breakouts occur constantly in stocks with no growth behind them
- Nothing distinguishes a leader from a name that merely moved
- No reason to expect the advance to be durable
- Institutional accumulation is invisible on price alone
CAN SLIM's actual claim is that the combination is the signal: a company whose numbers have already changed, at the moment the chart shows large buyers acting on it.
Both columns above are marked as costs, because both are. The system is not fundamentals with a chart bolted on for timing — it is an argument that the two together identify something neither can see alone, which is a fund quietly building a position in a company whose earnings have inflected.
Five ways into this system
- CAN SLIM letter by letter: what each test measures and where it is usually fudgedSeven tests, the numbers O'Neil attached to each, and the specific way each one gets quietly relaxed when a stock you like fails it.9 min read
- The 7–8% loss rule: what it is measuring, and why copying the number is not enoughThe most-copied rule in the system, and the one most often copied without the thing it depends on: a specific, defined entry price.7 min read
- CAN SLIM needs a growth cycle, US-quality data, and two hours a weekThis is the most data-hungry system in the library and the most sensitive to the market regime. Both facts narrow where it can honestly be run.6 min read
- The failure sequence: multiple compression, stop after stop, and the temptation to drop MThe system does not fail dramatically. It fails as a run of individually correct 8% losses, which is much harder to sit through than one large one.7 min read
- CAN SLIM for beginners: what the seven letters mean in plain EnglishSeven letters, explained without assuming you know what earnings per share, relative strength or a base is.8 min read
The ideas behind it
This system assumes you already know these. Each one is explained from scratch in Investing 101.
Compare with
- Weinstein Stage AnalysisPut every chart into one of four stages, and only own the ones in Stage 2 — above a rising 30-week moving average, breaking out on heavy volume.
- Minervini SEPA Trend TemplateFilter for stocks already in a textbook uptrend, wait for their volatility to contract into a tight pivot, and buy the breakout with a stop close enough to size against.
These are documented methods described for study. Nothing here is investment advice, a recommendation, or a claim about future returns — every system on this page has losing periods, and the pages say where.
Reading about a system is not having one.
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