Background: Many breast cancer patients do not adhere to prescribed adjuvant hormone therapy. This pilot study explored symptom experiences and medication adherence behaviors. Methods: Eligible women were postmenopausal, had hormone receptor positive stage I-IIIA breast cancer, completed surgery, chemotherapy, and radiation, and were taking adjuvant hormonal therapy. Standardized instruments were used: Brief Fatigue Inventory, Brief Pain Inventory, Menopause Specific Quality of Life Questionnaire, Pain Catastrophizing Scale, Modified Morisky Medication Adherence Scale, and Beliefs about Medicines Questionnaire. T-tests were used to compare symptoms by type of medication. Pearson correlations examined associations between medication taking behaviors and symptoms. Results: 108 women enrolled: mean age 64 (SD 9) years, 81% white. Mean time from surgery was 46 (SD 29) months and on hormonal therapy, overall and current, was 41 (SD 30) and 26 (SD 20) months, respectively. 19% were taking tamoxifen and 81% an AI (30% anastrozole; 18% exemestane; 33% letrozole). 27% changed therapy. Reasons for change were pain (tamoxifen n=8 vs AI n=20), vasomotor symptoms (1 vs 1), osteoporosis (1 vs 3), and rash (1 vs 1). Significantly (p<.05) more fatigue, pain intensity, and pain interference were reported with AI compared to tamoxifen. Significant (p<.05) predictors of nonadherent medication taking behaviors were: greater fatigue (r=.28), pain intensity (r=.28), pain interference (r=.35), pain catastrophizing (r=.30), menopausal symptoms (r=.41), and medication concerns (r=.29). Type of medication and perceived medication necessity were not associated with nonadherent medication taking behaviors. Conclusions: Side effects and perceived side effect severity are associated with nonadherent medication taking behavior. Interventions to address perceived side effects may improve adherence to therapy.