The American Institute for Cancer Research (AICR) sponsored its third annual confer ence on nutrition and cancer. The theme was Diet and Cancer: Markers, Prevention, and Treatment. The conference was held October 29-30, 1992 at the Ritz Carlton Hotel in McLean, Virginia. This proceedings contains chapters from the platform presentations and abstracts from the poster presentations. Several chapters address each of four session topics: Retinoids as Differentiation Agents in Cancer Therapy, Biological Markers of Cancer Risk, Chemoprevention of Cancer by Non-Nutrients in Foods, and Nutritional Problems and Support in the Treatment of Cancer. The first three chapters discuss in detail different mechanisms by which retinoids influence differentiation and provide evidence to support their use in cancer therapy. In vivo and in vitro studies show the effects of retinoic acid (RA) on tumorigenicity and cellu lar/molecular events. A synopsis of data showing the involvement of the retinoblastoma (RB) gene in HL-60 cell differentiation induced by RA and 1,2S-dihydroxy vitamin D3 (VD) is presented. In SCID (severe combined immunodeficiency) mice injected with HL-60 3 human leukemia cells and gavaged daily with RA, the number of tumor sites and number of mice with tumors are reduced. All trans-RA induces myeloid differentiation in HL-60 cells. Similarly, VD3 induces HL-60 monocytic differentiation. In both cases an early down regulation of retinoblastoma (RB) gene expression precedes the differentiation.