In October 1977 clinical bluetongue broke out in Aydin province, western Turkey and spread to adjacent provinces in the autumn months of 1978 and 1979. The outbreak was caused by a virus of serotype 4 and appeared to occur in a totally susceptible population. It was eventually controlled by widespread use of attenuated type-specific vaccine. Bluetongue virus was isolated from sheep on several occasions and also from a calf with congenital arthrogryposis and hydranencephaly. This latter finding is discussed in relation to Akabane virus, a recognised arbovirus teratogen thought to be present in the same area at the same time.