The effect of infection with Trypanosoma vivax on pregnancy and post-partum cyclicity in ewes was investigated. Of the 5 ewes infected in the first trimester, 3 died without aborting and 2 after aborting. Intrauterine infection occurred in 2 of the foetuses removed at post mortem. Of the 5 infected in the third trimester, one ewe died without aborting, one lambed prematurely and 3 at term. Intrauterine infection occurred in one of the lambs born at term. None of the lambs were viable. The termination of pregnancy may be as a result of stress. The ewes infected in the third trimester commenced irregular cyclicity 13 to 23 days post partum.