This review of the literature indicates that weight gain is a common observation among women after the diagnosis of breast cancer. Gains in weight range from 0 to 50 lb and are influenced by menopausal status; nodal status; and the type, duration, and intensity of treatment. Weight gain appears to be greater among premenopausal women; among those who are node positive; and among those receiving higher dose, longer duration, and multiagent regimens. Psychosocial research suggests that weight gain has a profoundly negative impact on quality of life in patients with breast cancer. Recent findings also suggest that weight gain during therapy may increase the risk of recurrence and decrease survival. Although weight gain in patients with breast cancer is clinically well appreciated, little research has been conducted to investigate the underlying mechanisms of energy imbalance. Changes in rates of metabolism, physical activity, and dietary intake are all plausible mechanisms and call for more research. Further study will provide valuable insight into the problem of weight gain and encourage effective interventions to improve the quality and quantity of life for the woman with breast cancer. Until more is known, however, dietetics practitioners will have to monitor and work individually with patients with breast cancer and use empirical approaches to achieve the important goal of weight management.