Pharmacist-written recommendation letters to physicians, through mail or fax, are common practice in managed care settings. While rates of physician acceptance of pharmacist recommendations have been reported to average around 50%, the factors affecting the provider's acceptance of recommendations have not been adequately explored. Identifying these factors may help to improve pharmacist-physician communication and help identify areas where physician education may benefit patient care. To (a) determine the percentage of pharmacist-written recommendations for members enrolled in a Medicare Advantage Plan with prescription drug coverage that was accepted by providers and (b) examine member and provider factors associated with provider acceptance. A retrospective cohort study was conducted among members enrolled in a Medicare Advantage Plan in Texas. Members were included if their medication profiles were reviewed by a health plan resident pharmacist and resulted in a recommendation letter sent directly to the member's provider between July 1, 2012, and March 15, 2014. Pharmacist-written recommendation letters were retrieved from the archived files and were assessed for factors such as type of recommendation made, the member's disease state affected by the recommendation, and the letter format. Other factors assessed included member and provider characteristics such as demographics, participation in the health plan pay-for-performance program, physician specialty, and region of practice. Acceptance was defined as a change in pharmacy claims that reflected the change suggested in the letter within 6 months of the recommendation. The percentage of recommendations accepted by providers was calculated. Chi-square tests were used to examine group differences in recommendation acceptances with recommendation type as well as member and prescriber characteristics. Logistic regression was used to identify significant predictors of an accepted change. From 158 pharmacist-written recommendation letters, 228 recommendations were identified, of which 115 (50.4%) were accepted. Ninety-five (41.7%) recommendations were to add a drug; 80 (35.1%) recommendations were to discontinue a drug; and 53 (23.2%) recommendations were to change a drug. The member population affected by these recommendations had a mean [SD] age of 69 [± 11] years. Recommendations to discontinue or change a drug were more likely to be accepted than to add a drug (P = 0.007), but recommendation type was not determined as a significant predictor in the multivariate model. Recommendations for heart failure were less likely to be followed compared with recommendations for diabetes (OR = 0.31; 95% CI = 0.10-0.96; P = 0.043). A regional trend was identified in which recommendations in Southeast Texas were more likely to be implemented than those in West Texas, but it did not reach a level of significance (OR = 0.51; 95% CI = 0.24-1.07; P = 0.074), possibly because of the relatively limited sample size. Overall, pharmacist-written recommendations were commonly accepted by physicians. Recommendations for heart failure were less likely followed versus those for diabetes. Since most recommendations for heart failure concerned changing drugs within the beta-blocker class, physicians may not have seen the value in modifying current therapy. This finding points to a potential need for physician education. Further research with larger samples is warranted to increase the power to identify significant differences in other variables that may need to be addressed in order to increase the rates of recommendation acceptance and improve patient care.