A service for identifying opportunities for drug cost savings in managed care plans and intervening by giving drug information to physicians is described. A clinical pharmacy company developed a computerized drug-use-review program to (1) identify and track variances in prescribing from drug-use criteria, (2) formulate plans for correcting the variances, and (3) document the impact of those interventions on drug costs. The software program weights prescriptions claims data against drug-use criteria to identify opportunities to save money. Savings opportunities for drug costs are defined as the net difference between the cost of the prescription claim and the lower, criteria-based cost. Episodes of potential savings are grouped by variables such as drug, physician, patient, and pharmacy, and each group is characterized by its total potential for cost savings. The groups are ranked to identify drug therapy problems that most contribute to the cost of medication misuse to the client. Pharmacists counsel identified physicians and enter the responses into a database for economic analyses. From September through December 1993, the software program was used to review 167,684 prescription claims totaling $4,368,576 in drug expenditures for enrollees in Pennsylvania's Pharmaceutical Assistance Contract for the Elderly program. Potential drug cost savings totaling nearly $280,000 were identified. Academic detailing by the company's pharmacists resulted in a saving in drug costs of more than $12,000 per month for the first three months after the detailing. Pharmacists at a clinical pharmacy company decreased drug costs for a managed care organization by using a software program to identify the drug costs with the greatest potential for savings and the physicians associated with those costs; the physicians were targeted for academic detailing.