OBJECTIVES: 1) To determine costs and utilization incurred by employees following enrollment in an employer-sponsored medication therapy management (MTM) program and 2) to assess the impact of attrition on health care expenditures METHODS: A longitudinal study using medical claims. Study participants were Lucas County employees with diabetes, hypertension and/or hyperlipidemia participating in an employer-sponsored open-enrollment MTM program. Claims for office, emergency room and inpatient visits were analyzed for the period of January 2005-July 2010. Disease-related expenditures were tracked for a period of two-year pre- and post enrollment. All expenditures were calculated as average costs per-patient pre and post joining and also as total expenditure borne by the employer. Dropouts were identified from an appointment database. Expenditures were calculated using claims for one year before and after the dropout date.  RESULTS: Claims were received for 361 employees that enrolled in the MTM program. Office visit expenses went down by $71,442.29 or by 22.36% after joining the MTM program. An increase in spending for emergency room visits by $12,597.16 was observed, there were no recurring post-enrollment visits and those that occurred were for indications that could have increased long-term spending for the employer. Total expenditure on inpatient visits went up by approximately $7600 but the amount spent on each visit went down from $7,746.36 ± 4,169.13 to 4,408.07 ± 6,204.77.Number of employees who had an inpatient visit increased from 3 to 7, with no recurrence of pre-visit events.  A decrease in total health care expenditures by over 14% was observed. Preliminary analysis for the second objective shows that on average employees spent $406.97/patient/year more when they dropped out of the program than if they stayed enrolled.  CONCLUSIONS: Pharmacist led MTM-program helped reduce health care expenditure for the employer. Improving retention for the program could help substantiate these cost savings.