SUMMARYMeasles surveillance data in Blantyre, Malawi were reviewed for 1996-8 to describe the epidemiology of infection and to estimate vaccine efficacy (VE) by the screening method. A total of 674 measles cases were reported to the Blantyre District Health Office during this period. Age distribution showed that 108 (16n1 %) of the cases were aged less than 1 year. The median age was 5 years. Eighty percent of the cases between 1 and 19 years had been previously vaccinated. VE was 68n6 % (95 % CI, 52n7-79n2) for children 12-23 months of age and 67n3 % (95 % CI, 48n3-79n3) for infants 9-11 months of age. Reasons for this low vaccine efficacy are discussed. Previous vaccination history was negatively associated with the risk for developing cough during measles infection (odds ratio (OR), 0n30 ; 95 % CI, 0n09-0n91), diarrhoea (OR, 0n64 ; CI, 0n44-0n95) and pneumonia (OR, 0n40 ; CI, 0n25-0n62). Logistic regression analysis showed that pneumonia in adults was negatively associated with vaccination history. The passive surveillance system for measles in Malawi was useful to describe the epidemiology of measles.