BOSTON (AP) Biologists will square off against theologians Thursday at the Statehouse as the Legislature launches its first in-depth debate about the use of cloned embryos to conduct stem cell research.

Sen. Cynthia Creem, D-Newton, has proposed an measure that would make Massachusetts the second state in the nation to authorize such research, while imposing a ban on reproductive cloning. Currently, state law does not address the issue of cloning.

The benefits, she said, would be measured in both medical advances and economic growth.

''We want biotech companies to feel comfortable doing their research here,'' Creem said. ''It could also save people's lives or improve the quality of life for people who are inflicted with diseases.

An opposing bill, proposed by Rep. Christopher Fallon, D-Malden, would ban all forms of human cloning a prohibition that Michigan and Iowa have already adopted, according to the National Conference of State Legislatures.

''Embryonic stem cell research turns human life into a commodity,'' said John Piccone, lobbyist for Massachusetts Citizens for Life. ''You're lowering the bar for what it means to be alive.''

Piccone will gather together a panel of bioethicists and clergy to combat Creem's proposal at a public hearing Thursday before the Legislature's Health Care Committee.

Scheduled to testify in favor of stem cell research, Creem said, is Travis Roy, a Boston University hockey player who was paralyzed in 1995 during his first collegiate game.

Stem cell research has shown promise to treat a host of diseases, from Alzheimer's and Parkinson's to spinal cord injuries to Lou Gehrig's disease. Because it often involves the destruction of embryos, however, it has become a new frontier in the national debate over reproduction and the beginning of human life.

In 2001, President Bush severely restricted federal funding for human embryonic stem cell research to a select number of existing cell lines. He has called for a ban on human cloning, both reproductive cloning to make babies and the cloning of embryos solely to cull stem cells for medical research.

The U.S. House passed a bill that would ban all human cloning, but the U.S. Senate has taken no action.

In this uncertain environment, with nearly half the states considering bills banning cloning, biotech companies need assurances from Massachusetts leaders that any investment they make here will not soon be rendered worthless, according to scientists and many business leaders.

''We're suffering under this political cloud because no one really knows what's going to happen at the federal level and there are still certain elements in the state who are opposed,'' said George Daley, a stem cell biologist with the Whitehead Institute and Harvard Medical School.

California is already reaping the benefits of its first-in-the-nation law authorizing research on cloned embryos, according to Creem and Daley.

Opponents of cloning said they believe research should focus on adult stem cells, rather than the destruction of human embryos.

''Any argument that says they should be sacrificed for research purposes further dehumanizes the status of those embryos,'' said Dan Avila, associate director for policy and research at the Massachusetts Catholic Conference.