The nonlinear material proustite (Ag3AsS3) has been employed in an optical parametric oscillator. The oscillator is pumped by the 1.06‐&mgr; output from a repetitivelyQ‐switched Nd : YAG laser and has signal and idler outputs near 2.1&mgr;. Operation of the oscillator is described and the results of optical parametric fluorescence experiments are given. The primary limitation on the operation of the oscillator is surface damage to the proustite crystal.