OBJECTIVE Tumor necrosis factor-alpha (TNF-alpha) exerts apoptosis throughout an intracellular transduction pathway that involves the protein kinases TRAF-2 (integration point of apoptotic and survival signals), signal regulating kinase (ASK-1) (pro-apoptotic protein), mitogen activated protein kinase-kinase 4 (MEK-4) (p38 activator and metastasis suppressor gene), Jun N-terminal kinase (JNK) (stress mitogen activated protein kinase) and the transcription factor activator protein-1 (AP-1). METHODS Biopsies from 20 normal, 35 hyperplastic and 27 carcinomatous human prostates were obtained for immunohistochemical and Western blot studies of the mentioned TNF-alpha/AP-1 transduction pathway members. RESULTS In normal prostates immunoreactions to TRAF-2, ASK-1, MEK-4 and JNK were positive, while no immunoreaction to AP-1 was detected. Although in benign prostatic hyperplasia the percent of immunostained specimens and intensity of immunoreactions to TRAF-2, ASK-1, MEK-4 and JNK decreased, the immunoreaction to AP-1 was positive in 27.3%. In most carcinomatous specimens the immune reaction was negative for all proteins of the TRAF-2/AP-1 pathway. CONCLUSIONS The TNF-alpha/AP-1 pathway might be a response to the excessive proliferative stimulus, although this response seems to be insufficient to counteract extracellular signals of cell proliferation. In prostate cancer this pathway is probably inactivated by other factors, such as p21 (at the ASK-1 level) or bcl-2 (at the JNK level).