The present paper reviews the possible utility and limitations of using behavior-modifying drugs to study reciprocal influences in parent-child interactions. Ideal circumstances for use of this approach are outlined and contrasted with the current status of the field of psychopharmacology. Numerous limitations to the approach are found. Yet the utility of the design is demonstrated in several studies of stimulant drug effects on the mother-child interactions of hyperactive children, and in one pilot study of the effects of diazepam, an anxiolytic, on these same interactions. The major pitfalls to this approach will quite likely be overcome by future research and the development of safer, more highly specific behavior-modifying drugs.