Activated stellate cells are myofibroblast-like cells associated with the generation of fibrotic scaring in chronically damaged liver. Gene chip analysis was performed on cultured fibrotic stellate cells. Of the 51 human CYP genes known, 13 CYP and 5 CYP reduction-related genes were detected with 4 CYPs (CYP1A1, CYP2E1, CY2S1 and CYP4F3) consistently present in stellate cells isolated from three individuals. Quantitative RT-PCR indicated that CYP2S1 was a major expressed CYP mRNA transcript. The presence of a CYP2A-related protein and testosterone metabolism in stellate cell cultures suggest that stellate cells express specific functional isoforms of CYP of which a major form is CYP2S1.