A cross-sectional anonymous postal survey was carried out in a Department of Internal Medicine in order to assess physicians' knowledge about and attitudes towards clinical practice guidelines and to evaluate the role of age in determining their use and opinions. The study took place in a Swiss University Hospital where exposure to guidelines had been limited. The questionnaire was sent to the 174 physicians of the Department. The response rate was 67% (116/174). The spontaneous definitions of guidelines were heterogeneous and referred to information of uncertain validity. Most participants, especially the younger groups of junior and senior residents, reported using guidelines and were favourable to their development. Less favourable attitudes were observed among senior staff physicians and consultants. For instance, the latter more often held the opinion that guidelines are too rigid to apply to individual patients, were likely to decrease physician reimbursement and to hamper research (respectively, 32% vs 24%, 50% vs 31% and 18% vs 7% when compared with the opinions of residents). In conclusion, in a non-prescriptive hospital setting, where the development, dissemination and implementation of guidelines are emerging, the concept of 'guideline' was heterogeneous. Despite generally positive attitudes towards guidelines, the opinion of senior staff physicians constitute a barrier to their dissemination and implementation.