California has become the first US state to provide funding for stem cell research, medical experiments that involve human embryos.
California could become a world leader in the research
Voters have approved $3bn-worth of funding to last 10 years.
President Bush and religious groups had strongly opposed stem cell research on moral grounds.
Supporters of the research said it could help find cures for deadly diseases and spinal cord injuries.
The ballot was held in conjunction with the presidential vote was known as proposition 71.
Supporters said the ballot's approval was needed to get around funding restrictions imposed by the Bush administration.
The campaign won the backing of California's Governor, Arnold Schwarzenegger, despite the opposition of the president and the Republican party.
The issue, which remains divisive, became particularly prominent after the death of actor Christopher Reeve, a strong advocate of stem cell research.
If the measure is approved, California would be cleared to issue $3bn in tax-exempt bonds and set up an institute to oversee 10 years of research.
It would also establish the constitutional right to conduct stem cell research in California, while outlawing
research on reproductive cloning.
Backers of the campaign said the funding could push ahead scientific work on curing disease and make California a world leader on stem cell research.