In this study, we evaluated the antiproliferative effect of tocotrienols (T3) and the presence of a specific vitamin E metabolism in PC3 and LNCaP prostate cancer cells. These cell lines are able to transform tocopherols (T) and T3 in the corresponding carboxyethyl-hydroxychromans metabolites (CEHCs). The extent of this metabolism and the inhibitory effect on cell growth followed the order of magnitude alpha-T<alpha-T3<gamma-T<gamma-T3. The partial inhibition of gamma-T3 metabolism by ketoconazole did not influence cell proliferation. These early findings may suggest that the transformation of vitamin E to CEHC is mostly a detoxification mechanism useful to maintain the malignant properties of prostate cancer cells.