Purpose: Among breast cancer patients receiving adjuvant chemotherapy, weight gain is a common side effect that may decrease quality of life and potentially threaten survival. Weight gain during treatment is a problem that is clinically well appreciated, and one that has been studied by a number of investigators. Design: A literature review was conducted to address each of the following issues: (1) the prevalence and magnitude of weight gain in women receiving adjuvant chemotherapy for early-stage breast cancer, (2) factors that might affect the amount of weight gained, (3) adverse consequences of weight gain, (4) mechanisms potentially responsible for weight gain, and (5) current dietary intervention programs directed toward women receiving adjuvant chemotherapy. Results: Weight gain is associated with a number of adverse effects in breast cancer patients receiving adjuvant chemotherapy. Weight gains are exaggerated in premenopausal women and women receiving multiagent regimens. Little research has been conducted to investigate the underlying mechanisms that contribute to weight gain in this population. Conclusion: Interventions to prevent weight gain during adjuvant chemotherapy are underway; however, little research has been conducted to investigate the underlying mechanisms of energy imbalance. Although changes in resting metabolic rate, thermogenesis, physical activity, and dietary intake are all plausible, no firm data exist to support any of these mechanisms. There is a need for research that explores the relative contribution of each of these factors to energy imbalance, so that optimally effective interventions can be created and implemented to combat this problem. © 1993 by American Society of Clinical Oncology.