Six rams were inoculated subcutaneously with 2000 toxoplasma tissue cysts. Semen samples from these rams, and from three uninfected controls, were screened for the presence of infective forms of toxoplasma. Three of the infected rams produced infective semen, each on two occasions, between 14 and 26 days post infection (pi). Five of the infected rams showed a febrile response from the fourth to 10th days pi and their indirect haemagglutination titres rose sharply from 10 days pi; the sixth ram was seropositive before infection and showed no clinical or serological response. In the experimental infection studied there were no symptoms or haematological changes of possible diagnostic value. The production of infective semen was restricted to a brief period shortly after infection although observations were continued for over 90 days. It was concluded that venereal transmission was unlikely to be significant in the spread of ovine toxoplasmosis.