Fenneropenaeus merguiensis and F. penicillatus are commercially important species of Pakistan coast. The biochemical changes during maturation are important to know the specific requirement of shrimp for maturation and formulation of maturation diets. Among the biochemical constituents, particularly lipids play most significant role during maturation. Such studies have not been undertaken previously on these two species from the entire range of its distribution. The variations in proximate composition, lipid classes and fatty acid composition have been studied in both the species in mid gut gland, ovary and muscle at four different stages of maturation, i.e. immature; early maturing; late maturing and ripe. The biochemical constituents showed an increasing trend as the maturation proceeds, though the specific variations were found in the concentration of all of the constituents studied and their trend of increase in both the species. The variations were pronounced in the ovarian tissue, whereas, moderate variations were found in the mid gut gland and minimal in the muscle during maturity stages. Based on the results, maturations diets were also formulated for F. merguiensis.