Last December, over 100 stocks were featured in our Top Picks for 2007 report. Now, at mid-year, we turn to the 20 advisors whose picks showed the strongest gains to get an update on their previous picks, as well as a new favorite stock for the second half of the year.

Ken Kam, editor of Marketscope, chose two stocks in the Top Picks for 2007 report and both picks qualified him for our Top 20 Advisors. His selection of Valero Energy Corp. (NYSE: VLO) rose 48%. Here is his original recommendation for Valero and his current opinion on the stock.

In addition, Ken also picked Elan Corp. (NYSE: ELN) in our Top Picks 2007 report and its gain of 35% also qualifies among our Top 20 Advisors. Now, he is now re-recommending the shares as his current favorite for the balance of 2007.

The advisor explains, "Elan has been strong on rumors that Biogen (NASDAQ: BIIB) -- Elan's 50% partner for its multiple sclerosis drug Tysabri -- is interested in acquiring the company. Elan has also show recent strength on news that the company's Alzheimer's drug (AAB-001), which is partnered with Wyeth (NYSE: WYE), is being advanced to Phase 3 trials.

"When a stock makes a big move in a short period, there is a tremendous temptation to sell and 'lock in profits.' However, when the price move is accompanied with good news, the initial bump may be the start of a major move up. If you are too quick on the trigger, you may miss the bigger, longer term.

"As to the Biogen story, I never trade just because of a rumor. However, I'd note that the majority of Biogen's sales comes from Avonex, a multiple sclerosis drug that competes with Tysabri. Biogen gets 50% of Tysabri sales, but Tysabri's price is just about double that of Avonex.

"Therefore, as things stand today, whether an MS patient uses Avonex or Tysabri, Biogen gets the same revenue. If Biogen were to acquire Elan, however, a patient that switches from Avonex to Tysabri would generate twice as much revenue for Biogen.

"And, patients who switch to Tysabri from any other drug would have double the impact on Biogen's sales than they do now. In short, this acquisition can make a lot of sense for Biogen especially if its done before Tysabri sales ramp up.

"The main problem I see is that it would be a big acquisition for Biogen whose market cap is $16 billion -- roughly double Elan's. But, interest rates are low, and capital seems to be available to do deals of this size. If a deal is done, however, I suspect that it will involve Wyeth because of its involvement with Elan's Alzheimer's drug. That's why today's news on AAB-001 is so interesting.

"No Phase 2 results have yet been announced, but I infer that both companies must believe that the results are going to be positive or they would not be willing to spend the millions of dollars its going to cost to run the Phase 3 trial.

"A successful Alzheimer's drug would be a home run for Elan. About 18 million people worldwide currently have Alzheimer's, compared to 2 million who have multiple sclerosis. Judging just from the number of patient's, AAB-001's potential may be almost 10 times bigger than Tysabri's.

"That's why I think that if a deal to acquire Elan is in the works, it probably involves Wyeth as well as Biogen. A deal in which Wyeth ends up with 100% of AAB-001, and Biogen ends up with 100% of Tysabri makes a lot more sense than Biogen acquiring all of Elan on its own.

"Bottom line, I cannot be sure, but there may be some truth behind the rumors. In the meantime, I suspect that many people will decide to sell to lock in the strong recent gains. I would not be surprised if the stock gave back half of its recent rise. If it does, I'll be buying more."