Your stock just took a nosedive -- but don't panic. First, let's see whether it had good reason to fall. Sometimes, panic-fueled drops can make excellent buying opportunities. Here's the latest crop of cratered stocks that could provide a possibility for profit:

Stock

Motley Fool CAPS Rating (out of 5)

Tuesday's Change

Amylin Pharmaceuticals (Nasdaq: AMLN)

***

(46.7%)

Marshall & Ilsley (NYSE: MI)

**

(10.2%)

Intuitive Surgical (Nasdaq: ISRG)

****

(7%)

On a day when the markets reversed course and jumped 129 points, or 1.2%, stocks that went in the other direction are big deals.

The devil's in the details
The Food and Drug Administration now seems more manic than the market's daily fluctuations. Amylin Pharmaceuticals got crushed, losing almost half its market value, when the agency rejected its diabetes drug Bydureon; the FDA said the drug needed more testing. Analysts were blindsided by the ruling, though some smart Fools urged caution. Wall Street thought Bydureon was a cinch for FDA acceptance, disagreeing only about whether Amylin's sales projections were too aggressive.

Novo Nordisk (NYSE: NVO) manufactures Victoza, the drug Bydureon was going to challenge upon approval. Novo had sales of $55 million in the second quarter, down 20% from the first. At least one analyst estimated that Bydureon would generate $420 million in sales annually for Amylin next year, with others pegging it at around $1 billion annually. Now, given the FDA's ruling and Amylin's inability to respond to the agency until late next year, Novo could enjoy an 18-month window to expand its lead. Little wonder Novo's shares rose 11% yesterday.

Yet the carnage wasn't Amylin's alone to bear. Both Eli Lilly (NYSE: LLY) and Alkermes (Nasdaq: ALKS) were Bydureon development partners. Their shares joined in the rout, falling 4% and 28%, respectively.

As is typical following such a bloodbath, many investors will move in, thinking the sell-off was overdone. CAPS member glennwhiteside thinks the nearly 50% drop in Amylin's shares qualifies as an overreaction. So does irishred1, who feels he's "scooping up bottoms" by getting in at this low price.

Only you can decide whether Amylin Pharmaceuticals is right for your portfolio. Add it to your My Watchlist page, where we aggregate all the Foolish news and analysis about this stock just for you.

The sky's not the limit
Financial services provider Marshall & Ilsley also took it on the chin yesterday. The company's earnings missed analyst revenue expectations, even though losses narrowed from the year-ago period. Yet as I pointed out the other day when discussing the results of Citizens Republic Bancorp (Nasdaq: CRBC), the gains Marshall & Ilsey made resulted from reductions in its loan loss reserves, in this case by 25%.

At least for Marshall & Ilsley's, the cutback seems warranted. While net charge-offs increased 5% from last year, non-performing assets dropped 22%, and the number of loans delinquent for 90 days or more fell 43% year over year.

The CAPS community somewhat supports Marshall's efforts to put itself back on a firm financial footing, with 75% of the members who've rated the company believing it will outperform the broad market averages. Let us know in the comments section below or on Marshall & Ilsley's CAPS page whether it's worth depositing your investment dollars.

Bad news from the surgeon
An earnings report that missed expectations also hurt Intuitive Surgical. Even though revenue rose 23% and earnings beat the Street's forecast, sales were weaker than anticipated. Analysts had been expecting $349 million, but Intuitive's sales were "only" $344 million, as more da Vinci systems were sold and more procedures using the device were performed.

This would appear to be one of those cases where the market exaggerated the magnitude of the miss, and sold off the stock as a result. CAPS member Freedy101 said he's been waiting for just such an occurrence, and that now is a good time to establish a position.

How about you? Is it time to get into Intuitive Surgical's stock, or should it be surgically removed from your portfolio? Diagnose the situation on the Intuitive Surgical CAPS page today.

Ready for a resurrection
Just because your stock has taken a beating doesn't mean it'll roll over and die. Markets are known for overreacting. A closer look at what's happened to your stock can give you an edge over other investors who just react to the market's lead.

That's why it pays to start your own research on these stocks on Motley Fool CAPS, where you can read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made, all from the stock's CAPS page. Then you can decide for yourself whether it's ready to come back from the dead.

Intuitive Surgical is a Motley Fool Rule Breakers recommendation. Try any of our Foolish newsletter services free for 30 days.

True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community.

Fool contributor Rich Duprey currently does not own any stocks as you can see here. The Motley Fool has a disclosure policy.