Cancer 'chemoprevention' uses substances to reverse, suppress or prevent the initial phase of carcinogenesis or the progression of neoplastic cells to cancer cells. Here it is shown that treatment with TRAIL proteins and all-trans-retinyl acetate can cause the death, in vitro and in vivo, of premalignant cells deficient in the adenomatous polyposis coli gene. Normal cells are unaffected. Selectively eliminating premalignant tumour cells in this way is thus an effective method for chemoprevention