Abstract: Expressed sequence tag (EST) analysis is an efficient tool for gene discovery and for profiling geneexpression. In order to isolate specific functional genes involved in reproduction and endocrine regulation and to reveal their evolutionary mechanisms in Chinese sturgeon (Acipenser sinensis Gray), a chondrostean fish with a history of 140 million years, we constructed its pituitary cDNA library from a 4 year-old male1 A total of 944 random cloneswere sequenced and compared with sequences in GenBank database1 Among all the 944 EST clones, 802 (84196%) clones were identified as 461 known genes, and additional 142 (15104%) as unknown genes. Functional categorization indicated that the most abundantly expressed functional gene was the proopiomelanocortin (POMC), which accounted for almost10117% of the overall expression, indicating its important function in the pituitary. Interestingly, the expression patterns of 7 unknown geneswere analyzed in various tissues, such as heart, liver, spleen, kidney, muscle, testes, ovary and pituitary. Three different categories of expression patternswere observed from them1 Several unknown ESTs, such as EG009334, EG009337, EG009338 and EG009340, were detected to be pituitary-specific, orpituitary and ovary-specific genes. Further　studies on their functions will be very useful for better understanding the mechanisms of sturgeon reproduction　biology and endocrinology.