OBJECTIVES:  To develop a tool to estimate the first-year per member and total health plan costs associated with fingolimod monitoring recommended by its Risk Evaluation and Mitigation Strategy (REMS). METHODS:   Data were incorporated into an interactive tool designed to allow a health plan to estimate their costs for monitoring.  The prevalence of MS was based on the literature.  Default values for the proportion of patients treated with immunomodulators and fingolimod were assumed and set at 95% and 1%, respectively.  Current Procedural Terminology (CPT) codes corresponding to recommended monitoring procedures were identified.  Charges associated with each CPT code were identified using software designed to build a physician fee schedule based on Medicare charges and default values were set at 150% of Medicare charges.  In cases where the REMS recommended that all patients undergo certain monitoring, default values were set at 100% for that monitoring.  In cases where the REMS recommended individuals with specific characteristics undergo monitoring, a database analysis identifying all individuals with a diagnosis of MS in the i3 InVision Data Mart (Ingenix, Eden Prairie, MN) was used to estimate the proportion of patients who may require that specific monitoring. RESULTS:   The tool yielded average per patient and health plan costs expected with fingolimod monitoring.  The tool conservatively estimates that the average per member first-year monitoring cost for fingolimod is $1905.  Based on the default values, the estimated annual costs of fingolimod monitoring for a million member health plan is $18,458.  The initial cardiac monitoring was the largest contributor to the total cost of monitoring.       CONCLUSIONS:   Estimating the anticipated economic impact of fingolimod monitoring, based on its REMS, allows health plans to more closely assess the total cost of fingolimod therapy.  This tool allows health plans to individualize inputs to estimate the plan-specific economic impact of fingolimod monitoring.