Britain's Kate French won gold at the modern pentathlon World Cup in Sofia, Bulgaria.
French, who finished fifth at the Rio 2016 Olympics, claimed her maiden World Cup title in Egypt last March.
The 26-year-old was 11th in her first event of the year in Kecskemet, Hungary earlier this month.
"I'm very, very happy," she said. "I had a bit of a break at the end of last season so to be able to come back and do that, I'm over the moon."
Natalya Coyle of Ireland took silver ahead of Russian Uliana Batashova.
London 2012 silver medallist Samantha Murray was 11th, with team-mates Jess Varley and Francesca Summers 22nd and 33rd respectively.
Britain's Tom Toolis, Sam Curry and Jamie Cooke will all compete in the men's finals on Saturday.