More than 1.5 billion prescriptions were dispensed from retail pharmacies in 1984 at a consumer cost of $18.4 billion. The number of prescriptions dispensed in 1984 equaled the previous record set in 1973. Over 40% of 1984 prescriptions were for four therapeutic classes: cardiovascular drugs, anti-infectives, psychotherapeutic drugs, and diuretics. Prescriptions for cardiovascular drugs and diuretics increased substantially from 1975 to 1984, while prescriptions for psychotherapeutic drugs decreased. Outpatient use of systemic antiinfectives remained fairly stable over the 10-year period. Trends in the use of specific drug categories within these broad therapeutic classes were variable, as were patient age and sex distributions.