The recent reception for initial public offerings may have flattened, but the ripples from last year's IPO frenzy are still roiling the market.

With the steep decline in the Nasdaq composite index and a general aversion toward new issues, the number of IPOs this month is a fraction of the number from previous months. The number of companies coming off their post-IPO lockups, however, is expected to soar--further putting pressure on stocks. Lockup periods typically last several months and prevent company insiders from unloading shares. This month, lockups will expire on more than 60 companies, including Agilent Technologies, McAfee.com and Vitria Technology. The deluge makes May the second-busiest month this year. An expiration for a lockup is usually set for 180 days after the IPO. That gives insiders such as company executives and board members, as well as early investors such as venture capitalists and strategic investors, first opportunities to sell stock. Agilent, the closely watched Hewlett-Packard spinoff, will have 380 million shares available for sale May 16, according to the company's prospectus filed with the Securities and Exchange Commission. HP is the holder of those shares, and it has previously indicated that it plans to distribute them to shareholders midyear.