The investigation of noncollinear type II phase-matching parametric upconver-sion of CO2 laser in a silver thiogallate (AgGaS2) crystal pumped with a Q-switohed Nd:YAG laser is reported. The computer calculation of optimizing noncollinear angle at which the phase mismatch ΔK is equal to zero is performed. The conversion efficiency was found to be 16.1% for the pump laser of 6MW/cm2 power density in a crystal of 4.7mm long, and the converted radiation was first detected by using a Si avalanche photodiode SPD-052.