The costs and savings resulting from two pharmacy-based investigational drug services (IDSs) for fiscal year 1996-97 were studied. The costs and savings associated with IDSs at two joint institutions were calculated by adding the cost-avoidance figures (money that would most likely have been spent, but was not because of a specific intervention or program) to the money received from services charged to study investigators or patients and subtracting salaries and overhead costs. Only drugs for which the authors could obtain prices were used to calculate cost-avoidance figures. The number of doses of marketed drugs that were provided free or for which the pharmacy was reimbursed by a drug study sponsor between July 1996 and June 1997 was tabulated from pharmacy dispensing records for each study. Investigational drugs that were not marketed or for which no marketed alternative was available were not included in the cost-avoidance calculation but were included in the charges for IDSs. The total cost of IDSs at the two institutions was $249,112. Income (representing cost avoidance and payments received) totaled $2,958,774, giving the IDSs an overall saving of $2,709,662. The two disease categories with the largest cost-avoidance figures were AIDS and oncology. In total, there was a cost avoidance of $2.9 million in drug costs, which is equivalent to 8% of the institutions' annual drug budget for 1996-97. IDSs in two institutions accounted for a combined one-year saving of over $2.7 million, most of which was attributable to cost avoidance from not having to purchase study drugs.