The Danish programme to control bovine enzootic leukosis was initiated in 1959 and intensified in 1969. The programme has resulted in a sharp decline in total and relative numbers of leukotic tumor cases in adult animals. However, total eradication of bovine leukosis has not yet been achieved, and the statistics from recent years seem to indicate that the present programme based on haematological and histological examinations will control but not eradicate the disease. An immunodiffusion test based on an internal protein (p 24) antigen has been used experimentally. This test is a valuable tool in herd diagnosis, but it is not sensitive enough for accurate single animal diagnosis.