The hot corrosion of porous Ni-23Cr-xMo (0%, 4.5%, 9.0%, 13.5%, mass fraction) alloys tested at 750 degrees C under cyclic procedure was investigated in order to elucidate the effect of Mo addition on hot corrosion in the presence of NaCl. The hot corrosion experiments were performed at 750 degrees C in air with 4 mg cm(-2) NaCl deposit. The performance of the alloys was evaluated by the results of weight change kinetics. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to characterize the corrosion products. The results indicate that NaCl accelerated the oxidation of the alloys by chloridized elements Mo and Cr. Among the porous Ni-23Cr-xMo alloys, Ni-23Cr-9Mo alloy exhibited the best hot corrosion resistance due to the formation of NiO-NiCr2O4-Cr2O3 oxide scales. Furthermore, these oxide scales were confirmed more effective to protect the alloys after adding of Mo.