Laura Chinchilla has been elected Costa Rica’s first woman president.
The 50-year-old ruling party candidate joined thousands of supporters after first results showed she had won 47% of the votes counted, way ahead of her main opponents and above the 40% needed to avoid a run-off.
Centre-left opposition candidate Otton Solis won 24% of the votes counted and right-wing lawyer Otto Guevara garnered 21%.
Mr Solis lost by a whisker to current President Oscar Arias in 2006.
The opposition had criticised Ms Chinchilla as being a puppet of Nobel Peace Prize laureate Mr Arias; she is expected to continue his policies of promoting free trade and international business ties.
A graduate of Georgetown University, Ms Chinchilla served as vice president under President Arias and is socially conservative on issues such as abortion.
Her National Liberation Party bet on her past experience as public security minister and justice minister to win voters over on the issue of crime - a growing concern in the country.
Balloting took place calmly throughout Latin America's oldest democracy, which has no army, amid reports of high abstention rates.
Abstention was at 33.43%, according to initial results, of some 2.8m eligible to vote.
The elections again tested the organisational skills of the ruling party, which has dominated politics in Costa Rica for the past six decades.
Ms Chinchilla has promised to increase grants for poor students, expand the pensions for the poor and open daycare centres to support working mothers.
She follows in the footsteps of four female presidents in Latin America - in Chile, Argentina, Panama and Nicaragua - in a nation which has promoted positive discrimination to bring women to political posts in recent years.
President Arias is due to hand over to Ms Chinchilla on 8 May.