Phospholipase A2 (PLA2) is a key enzyme that initiates the arachidonic acid cascade responsible for the synthesis of prostaglandins and leukotrienes, compounds well known for their inflammatory properties. Inhibition of this enzyme may modulate prostaglandin and leukotriene tissue levels. Uteroglobin is a potent PLA2 inhibitor found in rabbit uterus, prostate, seminal vesicle, and tracheobronchial tree. Tissue from ten human patients undergoing prostatectomy was examined for presence of a uteroglobin-like protein. Seven patients underwent transurethral resection and three had an open prostatectomy. Preoperative diagnosis in nine of the 10 patients was benign prostatic hypertrophy. One suspected, poorly differentiated, adenocarcinoma was confirmed and one unsuspected, well differentiated, adenocarcinoma was discovered. Specimens were submitted for Western blot, electron microscopy with immunogold staining, radioimmunoassay, and immunofluorescence. Six patients had evidence of uteroglobin-like protein, three with high levels (greater than or equal to 1000 pg./mg. protein), two with moderate levels (75 to 250 pg.), one with a low level (less than or equal to 75 pg.). Uteroglobin-like protein was present in all three patients who underwent open prostatectomy and in three of the seven patients with transurethral resections. The uteroglobin-like protein level was 2.5 to five times greater in both prostatic utricle specimens. All four assays corroborated these results. Because rabbit uteroglobin coats sperm and masks spermatic antigenicity in the rabbit female genital tract, this report of biochemical and immunological evidence for uteroglobin-like protein in the human prostate may have implications for human male fertility.