Data indicate that nonadherence plays a major role in preventable rehospitalizations. The first step to improving adherence is determining the affecting factor. This article critically reviews the literature on factors affecting medication adherence in heart failure patients. Findings about effects of age, gender, race, and living status on adherence are quite inconsistent. Patients who believe taking medications is beneficial or who have no side effects are more adherent, as are those highly motivated to improve their well-being. Forgetfulness, social support, and patient-provider relationship are related to adherence. Providers seeking to increase adherence must consider patients' expectations for their health, their environment, their barriers to following prescribed regimen, and their understanding of their condition and how it relates to medication taking.