OBJECTIVE: To review factors related to health beliefs and behavior that affect treatment adherence, and to suggest behavioral strategies for improving adherence. DATA SOURCES: We conducted MEDLINE and PSYHLIT (January 1966–October 1997) searches of English-language literature pertaining to behavioral medicine and health behavior as they relate to treatment adherence. Additional articles from these sources and reference texts were identified. DATA EXTRACTION: All articles and chapters identified were considered. The most pertinent information, as judged by the authors, was selected for discussion. DATA SYNTHESIS: Health care is moving into an era of disease management, and practitioners will be called upon to help patients change health-related behaviors and to improve adherence to treatment. Fundamental to this new paradigm of practice is an understanding of behavior, its relationship to health, and methods by which it can be altered. Current concepts of health behavior have been heavily influenced by social learning theory, self-efficacy theory, and a biopsychosocial view of health and disease. The intent of this review is to provide clinicians with an overview of factors that affect health-related behaviors, as well as suggestions for helping patients to improve them. As illustrations, behavioral interventions used in patients with asthma are presented. CONCLUSIONS: Adherence to treatment recommendations depends on a complex interplay of many psychological variables. An understanding of these factors, and how behavioral techniques may be used, will help healthcare providers to assist patients in improving adherence.