The effects of brucellosis in 60 mature elk (Cervus canadensis) and over 72 of their offspring were determined over a 65-month period. Artificial infections were induced with Brucella abortus type 1 strain 2308. All 27 artificially inoculated and 96% of 24 naturally-exposed mature elk became infected with brucellosis. An additional five cow elk were used to examine the importance of venereal transmission. The average incubation period from artificial exposure until abortion was 89 days among seven cows, and the average incubation period from exposure to development of a serotiter was 39 days among 24 artificially-inoculated cows. The most probable route of infection was oral contact through licking or ingestion of contaminated materials. Fetal fluids, vaginal exudates and aborted fetuses were the most likely sources of contamination. The venereal route of transmission was unimportant. Abortion or birth of nonviable calves was the most important and frequent sign of brucellosis, and 48% of 29 cows lost their first calf following infection. Other signs were secondarily infected hygromata and synovitis in the lower legs. Most calves born alive to infected cows demonstrated a serologic titer at or soon after birth, and the majority lost their titer. Many of the calves demonstrating early postnatal titers as well as those born without indication of infection became infected later in life. Although the maximum duration of brucellosis was not determined, one cow had maintained an infection for 56 months prior to necropsy. Five elk apparently recovered, but Brucella was recovered at necropsy from another three which also appeared to be recovering.