OBJECTIVES: To evaluate the economic impact of Specialist Outpatient Clinic (SOC) Pharmacy interventions METHODS: A retrospective study in Singapore General Hospital (SGH) SOC Pharmacy on the interventions made with physicians, between Aug 2012 and Oct 2012. Each intervention was analysed and assigned with an Estimated Cost of Avoidance (ECA) level, consented to by 3 pharmacists with varying clinical experience from 2 years to 15 years. The ECA level ranges from 1 to 8, with 1 having the least economic impact and 7 having the greatest economic impact. An ECA level of 8 has no economic impact as it signify non-acceptance of interventions by physicians. Subsequently, the economic impact per month is calculated by the total number of interventions in each ECA level, multiplied by the respective cost of avoidance, pre-determined for each ECA level based on national / institution standards, in Singapore Dollars. RESULTS: The economic impact of SOC Pharmacy interventions is estimated to be ~SGD 900,000 over 3 months, with an average of ~ SGD 300,000 per month. With an average of 23000 prescriptions per month, it is estimated that our SOC Pharmacy interventions saves ~ SGD 13 per prescription. Unlike traditional, direct methods to estimate the economic impact of pharmacy interventions, our results highlighted a great portion of cost savings to both institutions and patients, which are often neglected. CONCLUSIONS: Interventions performed by Pharmacy staff have a great impact on cost savings to institution and also patients.