Pursuant to our report of an immunoreactive and bioactive luteinizing hormone-releasing hormone (LHRH)-like molecule in rat spleen lymphocytes, we sought to determine whether these cells were capable of synthesizing LHRH by determining whether lymphocytes contain LHRH mRNA. To do this, total RNA was extracted from hypothalamic tissue, anterior pituitaries and from lymphocytes, and then this was reverse transcribed to cDNA and amplified via the polymerase chain reaction (PCR) utilizing synthetic oligonucleotides bracketing a portion of the LHRH gene. Following gel electrophoresis a discrete band of the expected size of 375 base pairs was found in the hypothalamus (positive control), and in lymphocytes, but not in the anterior pituitary (negative control). Furthermore, after Southern blotting, a 32P-labelled LHRH cDNA, hybridized to the 375 base pair, was amplified in hypothalamus fragments and in lymphocytes, but not in anterior pituitary tissue. These data strongly suggest that LHRH, in addition to being an important neuropeptide, is an immune cell synthesized immunomodulator.