This descriptive study of temporal trends and geographical distribution examines the effects of prolonged low-intensity warfare on the community-based malaria control efforts. Nicaragua's post-1979 malaria control programme is based on community participation in health education and in mosquito breeding site drainage, expanded case finding, and increased availability of chemotherapy. Mosquito resistance and increasing costs have forced a reduction in the use of residual pesticides. The number of reported malaria cases in the country fell from 25,465 in 1980 to 15,702 in 1984, while the ratio of blood smears to total population increased from 86 to 137 per 1000 people. Malaria incidence in the eight states of the country under heaviest military attack in the current war was compared to incidence in the eight states least affected by the war. In the war zone there was a 17% excess in cases from August 1983-April 1985 above a 1974-82 baseline average, while there was a 62% decline in the number of cases in the non-war zone.