12(S)-Lipoxygenase (LOX) is regarded as a pro-tumorigenic enzyme and as a potential target for therapy and prevention of cancer so that the search for specific 12(S)-LOX inhibitors is part of drug development strategies. To facilitate the identification of specific 12(S)-LOX inhibitors we have created an assay cell line by introducing a12(S)-LOX expression vector into SW480 colorectal cancer cells. When arachidonic acid was supplied in the medium both transiently and stably overexpressing cells produced 12(S)-hydroxytetraenic acid (HETE) originating from the transfected gene at 4-5-fold the amount obtained from control transfectants. 12(S)-HETE production was 1913.7+/-17.2pg/ml and reached a steady state level 24h after addition of arachidonic acid. To demonstrate the models suitability of 12(S)-LOX overexpressing SW480 cells they were used to measure the inhibitory activity of the plant phenols baicalein, kaempferol, quercetin, nordihydroguaretic acid and resveratrol which are known for their chemopreventive as well as LOX-inhibitory activity in different tumour models. All 5 compounds inhibited 12(S)-HETE production at concentrations below those necessary for growth inhibition.