The new OptiMAL-IT(R) rapid diagnostic test for malaria was evaluated in 271 patients in Thailand with uncomplicated malaria between June and July 2002. The sensitivity and specificity for the diagnosis of Plasmodium falciparum parasites were 88% and 92%, respectively. For species other than P. falciparum, the sensitivity was 65% and specificity was 99%. The performance of the new test decreased markedly at low levels of parasitaemia.