Most autism has a genetic cause although post-encephalitis cases are reported. In a case-series (N = 20) from Tanzania, 14 met research criteria for autism. Three (M:F = 1:2) had normal development to age 22, 35, and 42 months, with onset of autism upon recovery from severe malaria, attended by prolonged high fever, convulsions, and in one case prolonged loss of consciousness. In four other cases (M:F = 3:1), the temporal relationship between onset of autism and severe infection was close, but possibly spurious since malaria is common in Tanzania and there were indications of abnormal development in the child or a family member. In seven cases, (M:F = 6:1) autism onset was unrelated to malaria. The excess of non-verbal cases (N = 10) is related to local diagnostic practice.