Abstract: Studies were carried out at Nuclear Institute for Food and Agriculture in July 2002 to find out the effect of different host and parasitoid density levels on the efficiency of Trichogramma chilonis. Eggs of Sitotroga cerealella were used as a host for Trichogramma chilonis. Four different host densities viz., 5, 10, 20 and 40 eggs were provided to single pair of Trichogramma chilonis. Percent parasitism was highest (48.25%) at 20 eggs/single pair, whereas percent emergence was highest (88.89%) from 5 eggs but all treatments were statistically similar. Female ratio was also highest at 5 eggs/female. The longevity was highest at 20 eggs/pair. So 20 eggs/pair were suggested for rearing at laboratory condition. For parasitoid density, four treatments e.g. 1, 2, 3 and 4 pairs of T. chilonis were compared against 50 eggs of Sitotroga cerealella. Parasitism percentage was highest at 4 pair of Trichogramma, which was 49.6%. Percent emergence and longevity remained similar among all the 4 treatments. Female ratio was highest at 3 pair (49.92%) therefore, 3 pair is suggested for about 50 eggs.