Ever look at a stock chart and see missing candle bars between days, or even intraday? Those are gaps.

What is a gap fill in stocks?

  • When a stock gaps up, that means it opened higher than it closed in the prior period; the opposite is true for gap downs.
  • Fill the gap is a strategy where you buy a stock when it gaps down and wait for prices to go up to “fill” the gap.
  • Gaps are due to a catalyst or news event, and halts trading while it is happening. It typically occurs premarket or during the after hours, but intraday gaps happen too.
  • Gaps are key regions that chartists like to look at for potential trades.

Gap fill stocks example

With that in mind, let’s look at an example of how to potentially trade a gap using basic support and resistance lines, and key levels.

For an example, look at this daily chart on Amphastar Pharmaceuticals Inc. (AMPH).

Source: TradingView

As noted here, the stock had two gaps down, each attributed to catalyst events. You could, therefore, potentially use these areas for trading; if a stock “fills” the gap, that means its price rises back to the level it maintained prior to the gap.

Thus, you could have potentially looked to buy and hold AMPH to play for gap fill stocks. Let’s assume you noticed the gap downs and saw how beaten up AMPH was, so you looked for a mean-reversion trade. Assume you got long the stock around $12.50 area.

Here’s a look at how that buy-and-hold swing trade would have worked out.

Source: TradingView

With biotech stocks, gap ups and gap downs occur after a catalyst event, such as data releases from clinical trials, or FDA approval announcements. Consequently, if you watch the chart around these events, you may find opportunities for gap-fill trades.

The Bottom Line

Gap fills have huge reward potential, if you get the timing right and are patient. Biotech and pharma are particularly ripe for gap-fill plays because the nature of their development processes creates catalyst events that can create gaps in the first place, but don’t just jump into any gap you see because not all of these voids get filled.


Kyle Dennis runs Kyle Dennis’ Biotech Breakouts (biotechbreakouts.com). He is an event-based trader, who prefers low-priced and small-cap biotech stocks.

Kyle Dennis

Straight outta college Kyle Dennis taught himself to trade, and then made over $7 million in trading profits by the time he was 28 years old. Kyle reveals how to find, track, and profit from lucrative trades for exceptional profits. Thousands of traders follow him every day to learn how to target these high probability trades.

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