Abstract: The objective of the study was to investigate the results of Novidium (Homidium chloride) (R) chemotherapy on the effects of Trypanosoma. vivax infection on pregnancy and reproduction in Yankasa (YK) and West African Dwarf (WAD) ewes, infected in their first, second and third trimester of pregnancy. Three groups of ewes, made up of six pregnant YK and six pregnant WAD ewes each, were assigned at random to first, second and third trimesters of pregnancy. A fourth group of three pregnant YK and three pregnant WAD ewes formed the controls for the study. The experimental ewes in the first, second and third trimesters of pregnancy, were infected by jugular vene-puncture with 2.0 mLof blood, containing 2x10 Trypanosoma vivax 6 on day 23, 52 and 102 of pregnancy respectively. The control ewes were not infected. Fourteen days post infection (pi), the experimental ewes in each trimester, were divided into two groups of 3 pregnant YK and 3 pregnant WAD ewes in each group. One group was treated with Novidium at 1.0 mg kgG body weight, while (R) 1 the other group remained untreated. Of the 3 YK and 3 WAD ewes in the treated and untreated groups in each trimester of pregnancy, 1 YK and 1 WAD ewe each from the second groups, were killed humanely at 21days pi and at the end of the first and second trimester of pregnancy. The results of the study showed that the infected YK and WAD ewes were susceptible to trypanosomosis. Very low foetal weights, partial and almost complete foetal resorption, abortions and mortality were observed in the infected-untreated YK ewes. While abortions of autolyzed foetuses, abortion of a live foetus and a case of dystocia were observed in the infected-treated YK ewes. Embryonic mortality and abortions were observed in the infected untreated WAD ewes, while delivery of healthy lambs and resumption of normal oestrus was observed in the infected-treated WAD ewes. The non-infected YK and WAD control ewes had normal gestation and delivery of lambs Chemotherapy completely ameliorated the pathogenic effects of T. vivax infection on pregnancy and gestation in the WAD ewes, leading to delivery of healthy lambs and resumption of normal oestrus and reproduction, in contrast to the YK ewes. The breed of ewe influenced the results of Novidium chemotherapy on the effects of T. vivax (R) infection on pregnancy and reproduction.