Anti-phosphatidyl choline antibodies (alphaPC) have been measured in adult patients from Orissa, India with Plasmodium falciparum infection of varying clinical severity. Significantly raised levels of alphaPC were observed in infected individuals in comparison with controls. The IgG alphaPC were found to be generally more than IgM alphaPC in most cases. The IgG alphaPC levels were significantly more in those cases of cerebral malaria who recovered fully after quinine administration in comparison with fatal cases not responding to quinine therapy, indicating a role for alphaPC in prognosis of adult cerebral malaria. There was no significant difference in levels of alphaPC IgG between non-cerebral and fatal cerebral malaria patients, indicating an absence of a direct protective role in the development of cerebral manifestations. Subgroup typing of IgG with alphaPC activity indicated IgG3 to be the predominant type, followed by IgG2, IgG1 and IgG4. A significant inverse relationship between serum tumour necrosis factor-alpha (TNF-alpha) levels and IgG1 antibodies with alphaPC activity was found, emphasizing the importance of alphaPC in modifying disease severity. These observations appear to give credence to recent reports in the literature indicating that toxic malarial antigens consist of phospholipids and that antibodies to phospholipids (alphaPL) inhibit such antigens in experimental systems.