Abstract: In the present study effect of intramuscular injection of Ovaprim-C was studied on the number of eggs kg-1, fertilization rate and hatching percentage during May, 2002 in fish hatchery Islamabad on silver carp, Hypophthalmichthys molitrix. Fish spawned successfully following a single dose of injection of ovaprim (LH-RH analogue) with 0.6 mL kg-1 for female and 0.2 mL kg-1 for male. Ova and milt were stripped simultaneously and mixture was stirred for 15-30 sec during which fertilization occurred. Hatching occurred within 18-32 h after fertilization. Regression analysis was applied to assess the body weight dependence of absolute and relative fecundity. It was observed that body weight has positive influence on absolute (r = 0.990) and relative fecundity (r = 0.708). Equations were developed to describe these relationships. If it is impossible to determine the absolute and relative fecundity directly, then these parameters can be determined from the body weight. The equations of these parameters are highly significant (p<0.001) and can be used to estimate the absolute and relative fecundity with a fair amount of accuracy.