Using data from the Health Insurance Experiment (HIE), this article examines use of over-the-counter drugs (OTC) in a general, nonelderly population. Families from six areas of the country were assigned to health insurance plans that varied in the amount of medical care cost sharing. Thus, the out-of-pocket prices of OTC relative to prescription drugs were experimentally varied. The sites were chosen to represent markets with differing access to physician services. Multivariate methods were used to relate OTC use (collected from biweekly health diaries) to cost sharing and demographic variables. The empirical results do not support the expectation that people assigned less generous insurance for prescription drugs substitute OTC for prescriptions. People with complete insurance coverage purchased more of both types of drugs, suggesting OTC are an adjunct to formal medical care, rather than a substitute for it. Better educated and more knowledgeable consumers used more OTC drugs and spent more of their drug budget on OTC products. That there was greater OTC drug use in HIE sites with poorer access to formal medical care suggests there was some substitution between formal care and self-care with OTC drugs. Overall, however, better financial access to formal care promotes rather than substitutes for OTC use.