Luteinizing hormone releasing hormone (LHRH)-like factor was detected in human seminal plasma by radioimmunoassay. The concentrations of immunoreactive LHRH in all semen samples tested (n = 46) ranged from 31 pg/ml to 71 pg/ml. Total content per ejaculate (pg) varied between 58 pg and 329 pg. There were no significant differences (p greater than 0.05) in the concentrations or total contents of immunoreactive LHRH-like factor between normospermic, oligospermic, and azoospermic semen samples.