With the increasingly advanced treatments offered in veterinary medicine, the need to evaluate not only the treatment itself but also the implications of the treatment for the welfare of the animal has become more apparent. Follow-up studies are important sources of information for veterinarians concerning the potential outcome of a treatment and some of these studies include a statement concerning the welfare of the animal involved. In veterinary medicine, the concept of animal welfare is often equated to health status, but it is important to distinguish between the success of the treatment in restricted terms, i.e. the health aspects; and the success in more global terms, i.e. how the general welfare of the animal is during and after the treatment. A qualitative analysis was done on 32 follow-up studies of veterinary treatment given to dogs and cats, making reference to the terms "animal welfare", "quality of life" or "well-being". The studies typically speak about "quality of life", and rarely define the terms used. The parameters used to assess animal welfare are primarily related to clinical aspects, while behavioural parameters for a broader welfare assessment - if used at all - are often crude. The assessments are made by animal owners, and sometimes also by veterinarians. These results have severe implications for the validity and sensitivity of such studies. Seen from an ethological point of view, most studies are lacking sufficient broadness and detail in the parameters used to provide a basis for animal welfare assessments beyond a clinical evaluation. Veterinarians and animal owners do not necessarily have the required ethological knowledge to assess animal welfare in a broader sense. And both may be personally involved and thus introduce a bias in the assessment. The development and validation of parameters and instruments for animal welfare assessment in a veterinary context is necessary and could benefit from the expertise, experience and more impartial position of ethologists. This work would be useful in both prospective and retrospective follow-up studies, and could support the assessments done on a daily basis by the practicing vet. As an inspiration for ethologists to get involved, suggestions are made of potential contributions from ethology to animal welfare assessment in a veterinary context.