Essential fatty acids (EFAs) and their metabolites, especially gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid and decosahexaenoic acid are known to induce apoptotic death of tumour cells. But the exact mechanism by which these fatty acids are able to induce apoptosis is not clear. Recent studies suggest that these fatty acids are able to induce apoptosis in cells over expressing cytochrome P450 following depletion of cellular glutathione and inhibition of carnitine palmitoyl transferase I (CPTI) activity. On the other hand, BCL-2 prevented apoptosis induced by these long-chain fatty acids, where as n-3 fatty acids suppressed ras expression leading to suppression of development of overt neoplasia. Phosphorylation of BCL-2 inhibits its ability to interfere with apoptosis and enhances lipid peroxidation leading to the occurrence of apoptosis. Tumour cells treated with long-chain fatty acids show increase in lipid peroxidation process, depletion of antioxidants and phosphorylation of proteins. Based on these results, it is suggested that long-chain fatty acids induce apoptosis by enhancing lipid peroxidation, suppressing BCL-2 expression possibly by phosphorylation and augmentation of P450 activity. Thus, these long-chain fatty acids may, infact act at the level of gene/oncogene expression in producing their cytotoxic action on tumour cells.