This study was developed to test whether prospective dietician counseling could abrogate the unwanted weight gain seen among women receiving adjuvant chemotherapy for resected breast cancer. It was also designed to examine predictive factors for weight gain in an exploratory manner. Premenopausal women starting adjuvant chemotherapy for primary breast cancer were recruited for this trial. After appropriate stratification, they were randomized to a group which received monthly dietician counseling primarily aimed at weight maintenance versus a control group (whose attending physicians and nurses told them about possible weight gain but provided no formalized dietician counseling). One hundred and seven evaluable women were equally divided between the two protocol arms. The median weight changes 6 months after start of chemotherapy were gains of 2.0 kg in the dietician counseling group versus 3.5 kg in the control group. The median changes in average calorie consumption were reductions of 120 versus 46 cal/day on weekdays and 196 versus 20 cal/day on weekends for the counseling and control groups, respectively. Study data suggest that more weight was gained by patients with higher Quetelet's indices (p = 0.01) and patients who had been on a diet in the preceding 6 months (p = 0.02). Routine prospective dietician counseling aimed at weight maintenance appeared to produce small but statistically insignificant reductions in both calorie consumption and weight gain in this group of patients.