Mid-IR laser sources are of great interest for many applications. One interesting way to reach such wavelengths is the frequency conversion using a nonlinear material. Thus, the crystal growth of AgGaS2 is presented in this paper. As often reported, it must be annealed to be as transparent as possible for optical applications. Nevertheless, traditional vacuum annealings are too much long and the mechanism occurring not so well understood. Here, a new method based on a combination of a static and a dynamic vacuum annealing is proposed as well as its mechanism. Thus, highly transparent AgGaS2 samples were obtained for further optical experiments. (C) 2009 Elsevier B.V. All rights reserved.