The majority (75%) of adult patients with uncomplicated Plasmodium falciparum and P. vivax malaria are positive for anti-phospholipid antibodies (aPLA) as demonstrated by ELISA using a panel of anionic and cationic phospholipids. The highest IgG and IgM binding was to the anionic phospholipids, phosphatidylserine (PS), phosphatidic acid (PA) and cardiolipin (CL), but excluding phosphatidylinositol (PI) to which only low antibody levels were found. Comparison of the mean IgG and IgM aPLA showed a trend for anti-PA > CL > PS > PC > PE > PI. Anti-PI levels were compared in two groups of African children, one group with non-severe and the other with severe (cerebral) falciparum malaria. Children with cerebral disease had significantly lower IgM anti-PI. The results are discussed with the view that serum-derived aPLA may have a role in 'anti-disease' immune responses. Their possible role in the opsonization and phagocytosis of parasitized erythrocytes and in thrombocytopenia is also considered.