In Vivo protein quality of green gram (Vigna radiata L. Wilzeck) infested with insect Callosobruchus chinensis (L.) at 20, 40 and 60 per cent level of infestation was estimated by feeding it to rats for 40 days. The effect of the incorporation of uninfested and infested green gram rats on feed intake, weight gain, protein efficiency ratio, feed efficiency ratio, true protein digestibility, biological value, net protein utilization, protein retention and on the weight of kidney, liver and spleen was observed. The inclusion of insect infested grains in rat's diet had a significantly (P≤0.05) adverse affect on the protein quality. With increase in level of infestation there was significant (P≤0.05) decrease in the values (P≤0.05) of parameters under study. Significant losses in the weight of the kidney, spleen and liver of rats were also observed. The insect infestation resulted in the deterioration of biological protein quality of the green gram.