Studies on changes in biochemical composition and calorific values (K.cal/g) in relation to body weight and sex have been made in a fresh water Indian major carp, Labeo rohita (Ham.). There is high statistical correlations between body weight (g) Vs. water, lipid, protein, ash content and calorific values in this fish. The males have lower protein content and calorific values as compared to females but the difference was statistically non-significant. The details have been discussed in this paper.