Abstract: By semi-quantitative RT-PCR method and Southern blotting technology, growth hormone (GH) gene expression was determined in extra-pituitary tissues of green sunfish, Lepomis cyanellus. After the condition of semi-quantitative RT-PCR was established, 12 tissues of 6 months old (larvae stage) and 1 year old (mature stage) male L. cyanellus were detected. The results showed that GH gene was expressed in muscle, gonad, gill, heart, brain, and kidney in different level besides pituitary gland, and that no GH expression was detected in spleen, liver and stomach. Unexpectedly and interestingly, GH expression in muscle of adult fish was distinctly higher than that of sexually immature fish. In addition, the transcript levels of GH mRNA in the gonad of larvae and adult fishes were high. The data presented here provide the first systematic report of universal GH gene expression in extra-pituitary tissues in fish, suggesting that GH through autocrine or paracrine pathway exerted its possible important local physiological function during development and growth of L. cyanellus.