Human prostate specimens from 25 patients provided 15 normal, four benign prostatic hypertrophy (BPH), and seven adenocarcinoma samples which were studied using a polyclonal antibody against prostatic specific antigen (PSA) and protein A-gold complex. Our study showed the presence of gold particles in cytoplasmic vesicles and granules, rough endoplasmic reticulum, and occasional lysosomal dense bodies in columnar or cuboidal cells of acini from normal, BPH and well-differentiated cancerous specimens, but not in the acinar basal cells. Some moderately differentiated and most poorly differentiated tumors contained undifferentiated neoplastic cells in which PSA localizations often were associated with membranous structures since specific cytoplasmic organelles were not differentiated. In prostatic stroma, invasive cells which were of differentiated type localized gold particles. In addition, some neutrophils and macrophages also localized PSA suggesting their role in phagocytosis of extracellularly released PSA in the stroma of BPH and cancerous samples. Thus far, the authors have not observed neutrophils and macrophages with gold particles in normal prostate. We suggest that neutrophils and macrophages were involved in transport of some extracellularly released PSA from the prostatic stroma or other metastatic sites to sera in BPH and cancer patients.