[Cancer in domestic animals.  II.  Epidemiology (author's transl)]. 
The epidemiology of tumours in domestic animals and its significance in veterinary.  Human and comparative oncology as well as studies along more basically analytical lines are reviewed.  The epidemiology of tumours in domestic animals is the economic importance, among others in view of the detection and control of virus-associated disease.  The zoonotic significance to man of a number of forms of leukaemia in animals is still hard to estimate.  Their role as signals would appear to be of importance in particular areas (China, Scotland).  Epidemiological studies gave the impetus to important virological and genetic investigations.  The requirements to be met by veterinary and comparative epidemiology of cancer are discussed.