We have compared the use of primary health care and the diagnoses at visits to doctors in the Spili Health Centre (SHC) in Crete and the Dalby Health Centre (DHC) in Sweden. In DHC more patients per 1000 population visited the doctors than in SHC. This was so regardless of age-group and sex, in fact more or less regardless of diagnosis. Other differences between the populations were: The diagnosis acute otitis media was more frequent in the Dalby children than in the Spili ones. The opposite was true of "head injuries" which were more frequent in the Spili boys. Visits to doctors for bronchitis was more frequent in the Spili men, maybe because of the extensive smoking habits of Cretan men. Visits for diseases of the musculoskeletal system were more frequent in DHC than in SHC. A hypothesis worth testing is that this was influenced by differences in the health insurance and sick benefit systems. Angina pectoris was fairly frequent in both areas but cardiosclerosis (including healed myocardial infarction) was more common in DHC than in SHC. Use of primary health care may be influenced by the need for health care in the population, the accessibility of the health care facilities, the costs for the patients, the quality of care as perceived by the patients and by other sociocultural factors. Comparative studies, even though fairly uncommon today, may be of use in generating hypotheses about the impact of different factors on the use of health care.