The correlation between environmental pollution and human health is one of the most important topics in public health. Environmentally-induced diseases generally show multifactorial etiology and their occurrence is dose-related; they can be included among the emergent diseases also in veterinary medicine. The epidemiological study of naturally occurring environmental diseases in animals, regarded as sentinel health events, can provide valuable information on agents being studied in human environmental epidemiological research. The epidemiologic aspects of naturally occurring diseases of domestic animals have so far received inadequate attention. Surveys have usually consisted of descriptive pathologic reports or of simple listings of case. There has been little or no attempt to relate the number of cases to the underlying population, thus there is little information on the prevalence rates of various animal diseases compiled according to age, breed, sex or environment. This paper reviews epidemiological studies of pet animals with spontaneously occurring respiratory diseases and attempts to determine the value of the animal in general and the dog in particular as a comparative model for environmental health.