A prospective study was conducted from January 1998 to November 1999 in a malaria-endemic area of Sri Lanka to determine the short-term impact of an acute attack of malaria on the cognitive performance of 648 schoolchildren attending grades 1 to 5 (mostly aged 6-11 years) in 4 schools. Three groups were studied comprising children with malaria, children with non-malarial fever, and healthy controls. Cognitive performance in language and mathematics at the time of presentation and 2 weeks later was assessed. At the time of presentation, children with malaria scored significantly less in both mathematics and language than children with non-malarial fever and healthy controls. Two weeks later, the mathematics and language scores of children with malaria improved but the scores were significantly lower than the scores of children with non-malarial fever (P < 0.001) and controls (P < 0.001). Having malaria was a significant predictor of cognitive performance after controlling for other confounding factors. These findings suggest that an acute attack of uncomplicated malaria causes significant short-term impairment of cognitive performance. The impairment persists for more than 2 weeks and appears to be cumulative with repeated attacks of malaria.