OBJECTIVES: The purpose of this evaluation was to identify the types of interventions made by clinical pharmacists, determine the cost avoidance of pharmacist interventions and incorporate the information into a new system at Grady Health System. METHODS: Two phases were required to characterize the type, cost avoidance and total number of daily documented interventions made by clinical pharmacists from April 1998 to July 2003. A third phase was used to evaluate interventions made from June 2004-May 2005. Interventions were classified by the intervention type, assigned cost avoidance and the assigned a probability of likely occurrence of an event without intervention. Data was collected in phase two of the evaluation to determine the average documented daily interventions per clinical pharmacist and the total cost avoidance of clinical pharmacist interventions for the department. RESULTS: A total of 1,871 (29.6%) of 6,311 documented interventions were reviewed. There was an average of 4.9 interventions per adjusted workday documented. The average cost avoidance of a documented intervention was $288. The daily adjusted work day cost avoidance was $1,411.20 or an annual cost avoidance of $338,688 for the 64 month time period. If extrapolated to the entire data set, the cost avoidance would be $1,798,567. In the second phase of the project, the average number of daily interventions documented by a clinical pharmacist was 5.5 (SD ±1.2) resulting in an extrapolated annual cost avoidance of $380,160 per clinical pharmacist. In the final phase of the project, the average number of interventions increased to 26.2/day or a total of 9,552 pharmacist interventions. The cost to the health system is $128,941 in pharmacist salary dollars with cost avoidance savings of $2,037,863. CONCLUSION: The return on investment of the system was $16 for every dollar spent on clinical pharmacy services. Each intervention saves $213 for the health system.