Prolonged haemolysis may accompany infection with Plasmodium falciparum.We observed prolonged haemolysis in 4 of 10 patients with this type of malaria after parasitological cure. IgM antibodies specific for the glycolytic enzyme triosephosphate isomerase were detected in these patients' sera. Clinical recovery and a decrease in haemolysis coincided with a fall in these autoantibodies. In vitro, affinity purified autoantibodies isolated from the sera directed against triosephosphate isomerase induced lysis of erythrocytes and activation of complement as shown by the51Cr release assay. We assume that autoantibodies against triosephosphate isomerase contribute to the development of prolonged haemolysis and anaemia in P falciparum malaria.