The vote, 238 to 194 with 50 Republicans in favor, fell far short of the two-thirds majority required to overturn a presidential veto, setting up a possible showdown between Congress and Mr. Bush, who has never exercised his veto power. An identical bill has broad bipartisan support in the Senate; moments after the House vote, the Senate sponsors wrote to the Republican leader, Bill Frist, urging him to put it on the agenda.

The House action is the first vote on embryonic stem cell research since August 2001, when Mr. Bush opened the door to taxpayer financing for the studies, but only with strict limits. The new bill permits the government to pay for studies involving human embryos that are in frozen storage at fertility clinics, so long as couples conceiving the embryos certified that they had made a decision to discard them.