In total, 926 individuals representing 69 different species of bovids, cervids and camelids from one Czech and ten German zoos were tested for antibodies against five viral and three bacterial pathogens that can be transmitted across species borders. In addition, the archived veterinary data of all bovids, cervids and camelids, kept at eight of the 11 zoos between 1998 and 2004, were reviewed. The results demonstrate that both malignant catarrhal fever and Chlamydophila psittaci were endemic in zoo ruminants in Germany. Epidemiologic factors are discussed that might have a qualitative implication for cross-species transmission within zoos. The factors included are population size, population density and exhibit type (single species/mixed species).