A study was undertaken to evaluate the efficacy of boric acid as grain protectant in cowpea and bengalgram against Collosobruchus chinensis (L.). Boric acid powder mixed with cowpea and bengalgram at 1.0 and 2.0 per cent concentrations and observed for 6 months. The residual Levels were found increased upto third month of preservation (258.50 ppm in cowpea and 279.50 ppm in bengalgram) and decreased thereafter. However, cent per cent adult mortality of C. chinensis was observed upto 6 months period. The residue levels of boric acid were the lowest (10.84 ppm in cowpea and 9.10 ppm in bengalgram ) with the treatments washing and cooking, of the different methods followed to eliminate the residue. The extent of elimination of boric acid residue by washing was 81 and 79 per cent and by both washing and cooking was 92 and 90 per cent when the cowpea and bengalgram grains were treated with boric acid at 1.0 per cent whereas at 2.0 per cent level, the residue levels can be reduced to 79,75 and 89,87 per cent by washing alone end by washing and cooking process, respectively.