The addition of fatty acids to the diets of tumour-bearing animals results in specific and defined structural modification of the tumour membrane lipids without disrupting the cell. Furthermore, fatty acids at higher concentrations may act directly as anticancer agents, and there is evidence of selective sensitivity of neoplastic cells. Similarly, experimental enrichment of the diets with specific lipids modulates carcinogen-induced tumorigenesis at the initiation or promotion steps, and in some animal models, the growth rate of established tumours. Therefore, anticancer therapies which utilise lipid-based strategies may be useful clinically. Although dietary strategies used alone may have some favourable effect, it seems likely that the combination of diet with anticancer drugs has the best possibility of providing the extent of cytotoxicity required for tumour eradication. Such combinations could take advantage of an additive effect of each, or could act synergistically such as by the influence of dietary fatty acid modification on drug transport. However, dietary lipids may also increase the toxicity of anticancer drugs to normal tissues and decrease the therapeutic index. Further research is needed to define the role of lipids in future chemotherapy.