PURPOSE: Weight gain is a common side effect of adjuvant chemotherapy for breast cancer - a side effect that decreases quality of life and also may decrease both disease-free and overall survival. This weight gain also is unique, since patients lose lean body mass while they gain weight. These body composition changes become apparent within six months of diagnosis. METHODS: We explored whether a clinic-based exercise program, which promoted a specialized program of strength training, aerobic activity and a healthful (=20% fat; fruit, vegetable and calcium-rich) diet could prevent body composition change among Stage I/II premenopausal breast cancer patients who would receive adjuvant chemotherapy. Dual energy x-ray absorptiometry was used to assess body composition at both baseline and at six-month follow-up. Data from patients participating in the intervention (N=9) were compared to data from historic patient controls (N=36). RESULTS: Mean changes (SE) in body weight and composition at 6 month follow-up were as follows among historic patient controls and intervention participants, respectively: body weight +2.2(.4) kg vs. -2.0(1.3) kg (p=.02); % body fat +1.8(1.6)% vs. -1.3(1.2)% (p=.002); lean body mass -0.3(.01) kg vs. +0.1(1.5) kg (p=.80); and fat mass +2.0(.3) kg vs. -1.2(1.5) kg (p=.04). CONCLUSION: Data from this pilot study suggest that exercise/diet interventions may yield promise in preventing adverse chemotherapy-induced weight and body composition changes among young women who receive adjuvant chemotherapy for breast cancer, and that further study is needed. Since over half of the women approached for this intervention study refused on the basis of time and travel requirements, interventions that utilize home-based approaches may be necessary to reach greater numbers and a greater diversity of patients.