An epidemiological study was undertaken to elucidate factors associated with pet ownership. The study utilized questionnaires that were mailed to a systematic random sample of 700 households in the city of Guelph and Eramosa township. Reasons for ownership were analyzed by factor analysis while differences between owning and nonowning households were investigated using logistic regression. Sixty-five percent of dogs and 71% of cats were neutered. Only 2% of urban and 3% of rural dogs had never been vaccinated, compared to 12% and 17% for urban and rural cats. Families that included preschoolers were less likely to own pets, as were those from an urban area. The highest scoring reason for ownership was "companionship," followed by "love and affection" and for the "benefit of the children". The highest ranked reason for nonownership was "pets are a problem when I go away," followed by "I don't have enough time to devote to a pet" and "poor housing".