Our findings from a previous study, that increased consumption of beta-carotene and vitamin C is associated with favourable prognostic indices in patients with breast cancer, have been borne out by our current study of patient survival over a 6-year period. The results of the current study point to beta-carotene consumption as the dietary variable most significantly associated with improved survival. Only one death occurred in the group with the highest consumption of beta-carotene, while there were eight and 12 deaths in the intermediate and lowest groups of consumption respectively. The possible antiproliferative effects of beta-carotene have been recognised for some time, with investigations being focused more recently on its derivative, retinoic acid, which has been found to improve differentiation in many tissues, including cell lines derived from mammary carcinomas. Retinoids have been associated with significant clinical responses in a variety of tumours, and chemoprevention trials using beta-carotene have been undertaken for many malignancies. However, beta-carotene has not yet been used in clinical trials to evaluate its potential for the treatment of breast cancer. A large-scale clinical trial is necessary to determine the effectiveness of beta-carotene in reducing the chances of recurrence of breast cancer, and in preventing the development of new cancers.