The IFA test is applicable for the determination of antibody levels to malaria. It has been shown to give a reliable indication of the malarial experience in populations endemic for malaria. Its usefulness lies primarily in serologic surveys. A wide range of homologous and heterologous antigens is available. Maximum percentage positive and mean IFA titers are obtained from sera collected in the period following the peak transmission season. Serum collection during that period is thought preferable.