The isolation of Sindbis virus from the blood of sentinel animals (chickens and ducks) in June and August was evidence for circulation of this virus in a biotope investigated in Western Slovakia. The vector of the virus may be the Culex pipiens or the Mansonia richiardii mosquito. Neutralizing antibodies against Čalovo and Ťahyňa viruses as well as Sindbis virus were found in the sera of sentinel animals.