leptin, hormonal product of the ob gene, is known to regulate food intake, energy metabolism and reproductive functions in mammals. The mechanism by which leptin affect male reproductive system, in contrast to its well proven effects in female fertility, has been a matter of debate. Expression of leptin and its receptor in some reproductive organs suggests that leptin has both endocrine and paracrine/autocrine effects on reproduction. Various evidences have pointed to a direct role of leptin in the control of rodent testicular function such as steroidogenesis and spermatogenesis. Thus, detection of leptin and leptin receptor mRNA in bovine testis will be the first crucial step to an understanding of its paracrine/autocrine effect on testes in cattle.In the present study, we showed leptin mRNA as well as its functional receptor (Ob-Rb) mRNA in whole testis of Holstein cattle using reverse transcription and polymerase chain reaction analysis. To confirm the first results, RT-PCR products were amplified with Nested PCR using inner leptin primer pairs designed on different exons. Based on our results, although we did not determine the exact cell source of leptin in testis, it suggests that besides its primary actions at the hypothalamic-pituitary level, leptin can has a direct role in testicular physiology using autocrine and/or paracrine mechanisms.