Background: The study objective was to examine the relation between combinations of chronic conditions in the same person and the volume and variety of health care utilization. Methods: Analysis of continuous Netherlands Health Interview Survey data (1990–1997). The study population consisted of adults (16 years and older) reporting at least one chronic condition from the following six disease clusters: musculoskeletal diseases, lung diseases, neurological disorders, heart diseases, diabetes, and cancer (n=13, 806). Health care utilization is categorized in terms of contacts in the preceding year with a general practitioner (GP), medical specialist, physiotherapist, home help and/or home nursing, and hospital admission. Utilization was adjusted for age, gender and year of interview. Statistical methods used are contingency table analysis and (logistic) multiple regression. Results: Almost one-fifth of the study population reported more than one chronic condition. Musculoskeletal disease, in addition to being the most common single condition, was found to be the condition most likely to occur with one of the remaining five disease clusters. Seven per cent reported not having used any services at all. Two-thirds of the study population used at least two different services in the previous year. In contrast, 26% of the study population reported comprehensive utilization patterns (GP and/or home care and/or physiotherapist and/or medical specialist and/or hospitalization: minimum of three types). Persons with more than one chronic condition reported having used more services, in terms of volume and variety, than those with only one condition. Conclusions: There is a strong association between comorbidity and the volume and variety of health care services that are used. Since many people have comorbid conditions, their use of health services is more complex than would be suggested by a one-disease approach. New disease management systems need to be developed to reflect the multiplicity of health care needs of the ...