Procedures for the diagnosis of Br. ovis infection in rams were evaluated by examining 10 rams artificially infected by preputial inoculation. Observations were undertaken at weekly intervals for 1 year to follow changes in clinical, bacteriological and serological findings. Clinical lesions were detected in 1 ram 3 weeks after inoculation and in all rams by 8 weeks; lesions were undetectable in 3 rams at the completion of the trial. The presence of inflammatory cells in semen samples was the earliest indication of infection being demonstrated in 2 rams at 2 weeks and in all rams by 8 weeks; subsequently 86% of samples were positive. Br. ovis was detected in semen smears from 3 rams at 4 weeks but only one in all rams (at 27 weeks); overall 52% of semen smears were positive from 4 weeks onwards. Br. ovis was cultured from semen of 5 rams after 4 weeks and from all rams at 5 weeks; therafter 97% of samples were positive. All rams developed significant titres to the CFT between 2 and 9 weeks; therafter the CFT was a reliable indication of infection in 6 rams, highly suggestive in 3 and unreliable in one. By 8-10 weeks all rams developed significant titres to the IHA which were then maintained in all rams for the remainder of the trial.