Nine groups of four 18- to 24-month-old rams were inoculated with Actinobacillus seminis by the following routes: intraconjunctival, intranasal, oral, intravenous, intramuscular, intraepididymal, vas deferens, intraurethral or intrapreputial. Eight similar rams were left uninoculated as controls. Systemic clinical signs were minimal and were confined primarily to the inoculation sites and the scrotal contents. Mild to severe epididymitis resulted from all the routes of inoculation except intraconjunctival and intranasal. Direct inoculation into the genital tract, especially into the cauda epididymis, was more effective. Intrapreputial and intraurethral inoculation led to ascending urethral infection, and inoculation into the vas deferens resulted primarily in descending infection of the accessory sex glands. A seminis was isolated from 11 of the 36 test rams (30·6 per cent); 26 of the 36 rams, some from each of the test groups except those inoculated intravenously, reacted serologically.