SAN JUAN, Puerto Rico (AP) _ A pediatrician who wants statehood for Puerto Rico was elected Tuesday night as governor of the United States' biggest and most populous territory.

Election returns also showed Dr. Pedro Rossello's pro-statehood New Progressive Party taking over the island's congress.

Thousands cheered and danced outside party headquarters in rain-dampened streets as Rossello, 48, declared victory over Victoria Munoz Mendoza, 51, of the governing Popular Democratic Party. Her party opposes statehood.

''Thanks for giving Puerto Rico a new hope,'' Rossello told the crowd.

Munoz, from a leading political family, had hoped to become Puerto Rico's first woman governor. She told her disappointed supporters: ''We gave battle. We now accept the new challenges and battles we must give.''

With 51.9 percent of polling places reporting, Rossello had 429,692 votes, or 50.5 percent, to Munoz's 389,946 votes, or 45.8 percent. Pro-independence candidate Fernando Martin had 31,557 votes or 3.7 percent.

Former Gov. Carlos Romero Barcelo led in a close race for the island's non- voting representative in the U.S. Congress. Puerto Ricans also voted for 27 senators and 51 representatives in the legislature, 78 mayors and hundreds of city council members.

Although they are U.S. citizens, Puerto Ricans do not vote for president.

Rossello has pledged to call a yes-or-no vote in 1993 on whether the island should become a state.

Much of his support came from residents seeking change from the eight-year administration of Gov. Rafael Hernandez Colon. Rossello pledged ''a tough hand'' on crime. More than 700 people have been slain on the island this year, ahead of last year's record pace.

''The people realize that the government wasn't responding to them,'' said New Progressive founder Luis Ferre, a former governor.

Munoz's party wants Puerto Rico to remain a commonwealth, while seeking to expand its self-government.

Surveys say Puerto Ricans are split between those who want statehood and those who favor staying a commonwealth, with fewer than 10 percent favoring full independence.

Munoz is the daughter of Luis Munoz Marin, who helped forge Puerto Rico's status as a commonwealth with U.S. citizenship rights for islanders, and the granddaughter of Luis Munoz Rivera, a Puerto Rican statesman.

The island, which now has a population of 3.6 million, was ceded to the United States by Spain in 1898.