Four groups of non-pregnant, first second and third trimester pregnant Zebu heifers were used to study and compare the clinical manifestations of Trypanosoma vivax infection. All the infected heifers developed clinical trypanosomiasis manifested by massive parasitaemia, fluctuating pyrexia, anaemia, dull hair coat, emaciation, jugular pulse and enlarged superficial lymph nodes. There were group variations in the severity of signs shown. Infected non-pregnant heifers and heifers in the third trimester of pregnancy developed a more severe form of the disease than pregnant heifers in the first and second trimesters of pregnancy.