A serological survey was carried out on human brucellosis in Rusizi plain in Burundi from october 1984 to september 1985: 1,087 human sera were investigated by means of the rose bengal test and the technic of Wright's sero-agglutination. It comes out of this survey that: the aggregate prevalence of positive serology is 6.6%; such a prevalence is significantly higher in professionally at risk people (7.9%) than in people contaminated by food (3.5%).