A cross-sectional serological survey of the prevalence of brucellosis in ruminants in the Region of Republican Subordination and Khatlon oblasts (provinces) in Tajikistan was conducted in May 2003. Sera from 13,625 ruminants involving 3513 households in 172 kishlaks (villages) were collected and screened by the rose bengal test. Doubtful and positive results were further tested with competitive and indirect elisas. The overall serological prevalences (95 per cent confidence intervals [cis]) were 5·8 per cent (5·2 to 6·4 per cent) for sheep, 5·5 per cent (5·0 to 6·0 per cent) for goats and 2·1 per cent (1·0 to 3·2 per cent) for cattle. The results show that brucellosis was a common disease of ruminants that was widely but unevenly distributed throughout the two oblasts. Seropositive animals were found in 119 of the 172 kishlaks (69·2 per cent [95 per cent ci 61·9 to 75·6 per cent]) and 14·4 per cent (95 per cent ci 13·3 to 15·6 per cent) of the 3513 households. Evidence of infection was also found in cattle kept for milk production in urban kishlaks in two major cities and in state-owned dairy farms.