The authors report the results of an epidemiological survey of bovine brucellosis in Mali, based on a relatively representative sample of 1,000 serum samples from 236 herds. The prevalence of infection in the herds, established by indirect enzyme-linked immunosorbent assay (ELISA) was 53% +/- 6.4. The proportion of animals infected was 23.3% +/- 2.5, falling to 22% when compared with the basic serum pool of 9,466 samples. This rate was relatively high in stationary herds in the semi-arid, sub-humid and arid zones. Four strains of Brucella abortus were isolated from cattle bearing hygromas.