OBJECTIVES: A regional health plan implemented a specialty pharmacy benefit with increased copayment/coinsurance for specialty medications.  Our objective was to measure and compare the change in adherence and persistence after implementation of the specialty benefit.   METHODS: Pharmacy claims for patients who chronically used anti-inflammatory, immunosuppressant, cancer, and multiple sclerosis medications were assessed.  The intervention group consisted of those whose out-of-pocket cost-share for specialty medications increased by at least $25 (per 30-day fill), and the control group consisted of those whose out-of-pocket amounts did not change.  Adherence, defined by proportion of days covered (PDC), was measured every 3 months for 12 months before and after the copay change.  Paired t-tests compared the adherence in the pre- vs. post-periods.  Individual growth model analysis evaluated the changes in adherence throughout the time periods.  Cox regression analysis determined the difference in persistence between groups after the copay change, controlling for age, gender, copay level, group, and pre-period persistence. RESULTS: There were 237 patients in the intervention group and 211 patients in the control group.  The PDC results varied by drug type; adherence decreased after the copay change in the intervention group for patients on anti-inflammatory, immunosuppressant, and multiple sclerosis medications, but remained consistent for patients on antineoplastics.  The growth model showed a small, but statistically significant decrease in PDC of 0.01 after copay changes (P=0.014).  The Cox regression analysis indicated that the estimated risk of discontinuing therapy increased for patients in the intervention vs. control groups (hazard ratio=2.35, 95% CI: 1.43-3.58). CONCLUSIONS: The move to the specialty pharmacy benefit allows for closer scrutiny of specialty utilization by pharmacists who actively monitor utilization and access.  Despite the minimal adherence decrease and significant persistence changes, the results indicated relatively more stability with the use of specialty medications than that reported with copayment/coinsurance increases for traditional pharmaceutics.