The relationships between ethology and veterinary medicine, and clinical ethology and clinical veterinary practice, are being discussed. Clinical veterinary ethology is defined as the science occupied with the diagnosis and treatment of primary behavior disorders, including behavioral causes for clinical disease and sub-optimal performance. For discussion of behavior problems, these are categorized into those with direct economic impact, those with indirect economic impact and those without economic impact. Examples for each category are reviewed. Problems with direct economic impact are flank biting, tail and ear biting, group aggression, pen fouling and savaging of piglets by the dam in swine; and non-nutritive sucking, urine drinking, the buller steer syndrome, milk sucking, and behavior contributing to lesions, teat jnjury and mastitis in bovids. Behavior problems with indirect economic impact include restlessness, mutual massaging, coprophagia and stereotypies such as bar biting in swine; preputial sucking and urine drinking in swine and bovids; and object and mutual licking, abnormal motor patterns, extended lying down intensions and tongue rolling in bovids. Abnormal behavior without economic impact is discussed in terms of welfare implications. Practical recommendations are made concerning the integration of behavior observations into a herd health program and regarding the solution of behavior problems. It is concluded that clinical ethology makes a significant contribution to veterinary practice, especially to herd health programs. More information is needed, though, especially relative to: (1) the epidemiology of behavior problems; (2) the economic effects of problems and their treatment; (3) the efficacy of treatments.