Many factors contribute to the success or failure of adjuvant therapy, but perhaps one of the most critical is treatment adherence. Patients do not adhere to prescribed therapy for a variety of reasons, and each one should be uncovered and addressed or managed accordingly to maintain therapeutic levels and give patients the best chance for positive outcomes. Nurses are well positioned to play a central role in promoting adherence by ensuring that patients understand the need for treatment and by identifying any underlying causes of nonadherence to therapy. When the issues are identified and addressed effectively, patients' chances for successful clinical outcomes are greatly improved. This article summarizes the issues surrounding adherence, paying specific attention to adjuvant endocrine therapy for breast cancer, and outlines strategies to reduce nonadherence that nurses can incorporate into clinical practice.