To date androgen receptor (AR) expression and structure in human prostatic cancer have been studied in primary tumor specimens and in cell lines. Investigation of alterations in the androgen-signalling transduction cascade in prostatic carcinoma metastases is important to improve our understanding of tumor progression towards androgen insensitivity. In the present study we have collected data comparing AR expression in both the primary tumors and the respective pelvic lymph node metastases. Formalin-fixed and paraffin-embedded tissues derived from the primary tumors and positive lymph nodes of 12 patients undergoing radical prostatectomy were immunostained for the AR and prostatespecific antigen (PSA). AR expression was evaluated with the polyclonal antibody PG-21, which is directed against amino acids 1-21 in the N-terminal region of the AR. All primary tumors stained for the AR. In 8 of the 12 lymph nodes examined more than 50% of the tumor cells were AR positive and displayed a uniform staining pattern; in one lymph node metastasis remarkable heterogeneity in AR expression was observed. In two cases less than 10% of the tumor cells stained for the AR. In one case the lymph node metastasis was immunohistochemically negative for the AR, whereas the primary tumor obtained from the same patient displayed intense staining for the AR. PSA was expressed in all metastases and primary tumors. Our data demonstrate that loss of the AR in lymph node metastases from prostatic carcinoma is a rare event.