The amino acid (AA) composition of different fully vitellogenic oocyte batches was determined. These oocytes were obtained from seven mature cultured Siberian sturgeon (Acipenser baerii) females with high reproductive potential and quality of their sexual products (fertilization rate 70-98%). Essential amino acids (EAA) represented 46-50% of the total AA content. Nonessential amino acids represented 47-54% of the total AA oocyte content. In all studied oocyte batches, leucine, lysine, arginine and isoleucine were the most abundant EAA, representing 27% of the total AA content. The AA composition of Siberian sturgeon oocytes found in the current study is similar to those determined in cultured white sturgeon (A. transmontanus) with the exception of threonine, proline, histidine and aspartic acid, which are 25 and 35% higher and 20 and 30% lower than in white sturgeon secondary oocytes, respectively. Differences in the AA profile between these two closely related species were detected and could be related to female age, stage of oocyte development, different broodstock management and feeding strategies, species-specific AA metabolism and/or trophic ecology. The results could be a valuable tool for determining nutritional requirements for first feeding larvae and a first step toward better knowledge of the nutrition and physiology of early life stages of Siberian sturgeon.