Epidemiologic investigations indicate a close relationship between colorectal cancer and fat intake. However, to date the effects of lipid peroxidation-derived products that are formed from fat (especially free or esterified unsaturated fatty acids) on the initiation or progression of colorectal cancer have not been investigated extensively. Therefore, in the present study, we examined the effects of fatty acids, fatty acid hydroperoxides and aldehydes on the growth of human colorectal cancer cell line HT-29. At concentrations of 1 and 10 μM, linoleic, arachidonic and eicosapentaenoic acids, and 13-hydroperoxyoctadecadienoic and 15-hydroperoxyeicosapentaenoic acids had no significant effects on the growth of HT-29 cells. 4-Hydroxynonenal and 4-hydroxyhexenal had no significant effects on the growth of HT-29 cells up to 10 μM, whereas 4-oxononenal potently inhibited HT-29 cell growth (1–10 μM, 16–85% inhibition). Further experiments concerning DNA fragmentation, expression levels of Bax and Bcl-2 mRNA, expression levels of pro-caspase-3 and caspase-3 proteins, and activity of caspase-3 suggested that 4-oxononenal may increase the sensitivity of HT-29 cells to apoptosis through a decreased expression level of Bcl-2 and then increased formation of caspase-3 from pro-caspase-3.