An analysis of claims data from a managed care health plan was performed to evaluate whether patients use chiropractic care as a substitution for medical care or in addition to medical care. Rates of neuromusculoskeletal complaints in 9e diagnostic categories were compared between groups with and without chiropractic coverage. For the 4-year study period, there were 3,129,752 insured member years in the groups with chiropractic coverage and 5,197,686 insured member years in the groups without chiropractic coverage. Expressed in terms of unique patients with neuromusculoskeletal complaints, the cohort with chiropractic coverage experienced a rate of 162.0 complaints per 1000 member years compared with 171.3 complaints in the cohort without chiropractic coverage. These results indicate that patients use chiropractic care as a direct substitution for medical care.