The aim of this study was to relate the working style of general practitioners to the health status of a sample of their patients. From a large regional sick fund forming part of the national health insurance system in the Netherlands a stratified sample was taken of general practitioners with at least 1000 patients on their list, taking into account the degree or urbanization of the area in which they practised and their annual referral rates to specialists. These 75 general practitioners were observed for two days in their surgeries by trained doctors and rated according to criteria defined beforehand. Taking into account these ratings and the annual figures from the sick fund for prescribing selected drugs and referrals to specialists, the general practitioners were classified into styles of practice - integrated, interventionist or minimal diagnostic. Twenty randomly selected women, aged 50-65 years, from each general practitioner's list, were interviewed and examined by independent doctors. The patients of general practitioners with the integrated practice style appeared to feel more healthy and to have more realistic expectations about the possibilities of professional help for common ailments. They tended to visit their doctor less frequently and to have fewer symptoms. The results showed an association between the quality of general practitioners and patients' health, and it may therefore be concluded that good general practitioners can further the health and well being of their patients.