OBJECTIVES To determine if dispending channel (specialty pharmacy versus retail) impacts medication adherence for patients receiving therapy for Multiple Sclerosis (MS). METHODS Retrospective pharmacy claims for MS patients were extracted for 2007-2008. Patients were followed for 12 months from the index claim. Adherence was measured using a Medication possession ratio (MPR), with patients considered adherent if MPR ≥ 80%. Propensity scoring was used in the sample selection. Differences of demographics were evaluated using the Wilcoxon signed-rank test for continuous variable and the chi-square test for the categorical variable. Generalize linear regression was used to calculate the adjusted mean adherence. RESULTS From a study population of 31,593 MS patients, a matched sample of 19,742 was chosen (9,871 in the specialty and retail channel). There were no differences in demographics between the samples, with 76.19% female and mean age of 48.84. Overall comparison showed an average MPR of 89.94% for specialty and 84.08% for retail; with 81.52% of specialty patients adherent (MPR > 80%) vs. 71.18% of retail patients. The results were similar for each individual MS therapy. The following list the drug, and the percent of specialty and retail patients at least 80% adherent: Interferon beta-1a (Avonex) 87.49% vs. 78.13%, interferon beta-1a (Rebif) 80.97% vs. 75.50%, interferon beta-1b 79.16% vs. 66.48%, glatiramer acetate 78.26% vs. 63.81%. (Average MPRs for each drug available on the poster.) All comparisons were statistically significant (P<.05). CONCLUSIONS Patients who receive their MS medication from a specialty pharmacy are much more likely to be adherent than those who receive medication from a retail pharmacy. This is true across the broad category, as well as each individual therapy. Specialty pharmacy offers enhanced patient counseling and clinical services, which may explain differences in adherence. Follow up studies will explore the impact of improved adherence on clinical and economic outcomes.