PURPOSE: To determine whether a low-fat diet high in vegetables, fruit, and fiber differentially affects prognosis in breast cancer survivors with hot flashes (HF) or without HF after treatment. PATIENTS AND METHODS: A secondary analysis was conducted on 2,967 breast cancer survivors, age 18 to 70 years, who were randomly assigned between 1995 and 2000 in a multicenter, controlled trial of a dietary intervention to prevent additional breast cancer events and observed through June 1, 2006. We compared the dietary intervention group with a group who received five-a-day dietary guidelines. RESULTS: Independent of HF status, a substantial between-group difference among those who did and did not receive dietary guidelines was achieved and maintained at 4 years in intake of vegetable/fruit servings per day (54% higher; 10 v 6.5 servings/d, respectively), fiber (31% higher; 25.5 v 19.4 g/d, respectively), and percent energy from fat (14% lower; 26.9% v 31.3%, respectively). Adjusting for tumor characteristics and antiestrogen treatment, HF-negative women assigned to the intervention had 31% fewer events than HF-negative women assigned to the comparison group (hazard ratio [HR] = 0.69; 95% CI, 0.51 to 0.93; P = .02). The intervention did not affect prognosis in the women with baseline HFs. Furthermore, compared with HF-negative women assigned to the comparison group, HF-positive women had significantly fewer events in both the intervention (HR = 0.77; 95% CI, 0.59 to 1.00; P = .05) and comparison groups (HR = 0.65; 95% CI, 0.49 to 0.85; P = .002). CONCLUSION: A diet with higher vegetable, fruit, and fiber and lower fat intakes than the five-a-day diet may reduce risk of additional events in HF-negative breast cancer survivors. This suggestive finding needs confirmation in a trial in which it is the primary hypothesis.