To determine age, breed, sex, body condition score, and diet of dogs and cats examined at private veterinary practices in the United States during 1995, and estimate prevalences of the most common disorders for these animals. Cross-sectional study. 31,484 dogs and 15,226 cats examined by veterinary practitioners at 52 private veterinary practices. Information on age, breed, sex, body condition score, diet, and assigned diagnostic codes were collected electronically from participating practices and transferred to a relational database. Prevalence estimates and frequencies for population description were generated using statistical software. Dental calculus and gingivitis were the most commonly reported disorders. About 7% of dogs and 10% of cats examined by practitioners during the study were considered healthy. Many conditions were common to both species (e.g., flea infestation, conjunctivitis, diarrhea, vomiting). Dogs were likely to be examined because of lameness, disk disease, lipoma, and allergic dermatitis. Cats were likely to be examined because of renal disease, cystitis, feline urologic syndrome, and inappetence. Results can be used by veterinary practitioners to better understand and anticipate health problems of importance in cats and dogs they examine and to better communicate with clients regarding the most prevalent disorders in cats and dogs.