A study was undertaken in the south- west of Western Australia to investigate potential vertebrate hosts of Barmah Forest virus ( BFV), Sindbis virus ( SINV) and Trubanaman virus ( TRUV) following isolation of these viruses from mosquitoes collected during routine surveillance for arboviruses. Over 3000 animal and human sera collected between 1979 and 1995 were tested for the presence of neutralising antibodies to each of the viruses. The overall prevalence of antibodies to BFV, SINV and TRUV was 0.4%, 0.3% and 1.6%, respectively. Antibodies to BFV were detected only in quokkas ( 3.2%), horses ( 1.2%) and humans ( 0.9%). No definitive evidence of infection with BFV was detected in samples collected prior to 1992, supporting previous suggestions that BFV was introduced into the region after this time. Antibodies to SINV were detected in western native cats ( 16.7%), emus ( 4.5%), rabbits ( 0.8%) and horses ( 0.7%), and evidence of TRUV infection was most common in western grey kangaroos ( 21.1%), feral pigs ( 3.6%), rabbits ( 2.4%), foxes ( 2.3%), quokkas ( 1.6%) and horses ( 1.6%).