Abstract The island of Mauritius entered in 1968 into the maintenance phase of its successful malaria eradication programme. Epidemiological criteria for interruption of transmission of the infection and elimination of remaining foci of malaria are usually based on microscopical examination of blood-samples for malaria parasites. In Mauritius, in addition to this procedure, indirect fluorescent antibody (I.F.A.) tests were carried out on over 6000 sera of inhabitants of Mauritius of various age-groups. The virtual absence of positive I.F.A. tests in children below the age of 5 years confirms the absence of transmission during the past 5 years and indicates the value of this serological method used in the field on a large scale.