A study of the nonlinear properties of cuprous halides in the near infrared (YAG Nd3+laser) and in the medium infrared (CO2laser) is presented. The second-order susceptibilities have been compared to those of quartz and GaAs. Coherence lengths were measured at 1.06 μ and for the four principal transition lines of CO2laser. In addition some linear parameters such as refractive indices in the visible and absorption coefficients from 0.3 to 25 μ were determined. The large values of Miller's δ14of those compounds are consistent with Levine's bond-charge model.