Tech stocks across the board had a down day Wednesday after a week of consistent gains, and biotech stocks weren't able to escape the decline. The Dow Jones U.S. Biotech Index had climbed 15.3% in the week leading up to yesterday's close, before slipping back 3.4% today. The index is up more than 39% since the recent Nasdaq low on April 4.

"It's similar to what we're seeing in the rest of tech," said Rob Cohen, the co-head of listed trading for Credit Suisse First Boston. "People put a lot of money to work over the last week. Buyers are just taking a breather."

Abgenix ( ABGX) fell hard today, losing 11.5% to $40.35. Human Genome Sciences ( HGSI) lost 6.4% to $68.46 today, while Gilead Sciences ( GILD), a company developing drugs to deal with infectious diseases, fell 6.5% to $54.04.

The Nasdaq Biotechnology Index had added 17.8% during the last week, and 53.2% since April 4, but it fell 3.8% today. Cohen noted that the moves weren't attended by "a lot of volume or heavy selling."

Millennium Pharmaceuticals ( MLNM), one of the biggest biotech gainers in the last week, climbing by 34.7%, lost 5.7% today to $41.80. Imclone Systems ( IMCL), which was all over the press last week for its research announcements coming from the American Society of Clinical Oncology conference, gained 23.4% in the past week, before losing 5.3% to $47.61 today.

Biogen ( BGEN) fell 6% to $59.79 today, while OSI Pharmaceuticals ( OSIP) dropped 5.8% to $48.10. The Nasdaq 100 Index, which includes a broad range of tech stocks, including biotechs, fell 3.1%. Amgen ( AMGN - Get Report) slipped 1.7% to $65.15.

One biotech notable headed higher today was Genome Therapeutics ( GENE), which rose sharply after a positive research report this morning from Ladenburg Thalmann. The firm, according to reports, rated Genome Therapeutics a strong buy, saying that the company is "a leader in using pathogen genomes to find anti-infective drugs." The firm also put an $84 price target on the stock. Shares of Genome Therapeutics traded for $13.05 earlier, a gain of 39.5% on the day.