Using a one-stage random probability sample of households, 5806 people in an area of Norway were interviewed about illness, use of medicines, self-treatment and visits to the doctor in the previous two weeks. Several social and demographic variables that might influence primary health care utilization were divided into five categories: need of medical care; self-care; availability of the doctor; sociodemographic factors; social network factors. Multiple classification analysis was used for the statistical analysis. The greatest influence on the percentage of people seeing the doctor was the need for medical care, the second largest influence was self-care. The availability of the doctor had a different effect according to whether the illness was chronic or non-chronic. Difficulties in reaching the doctor reduced the number of consultations for non-chronic diseases while the opposite was the case for chronic diseases. Among the sociodemographic variables neither level of education nor income had any influence on utilization when other variables were taken into account. Increasing age, however, caused a large increase in the percentage seeing the doctor, except after the age of 85 years when there was a large drop in consultation rate despite increasing illness. Social network factors had little effect on health care utilization.