Gas discharge tubes (GDT)-sometimes named spark gaps (SGs)-are commonly used to suppress transients in many applications, from high-frequency communications to ac medium-power supply lines. The sharp GDT breakdown characteristics enable them to provide suitable transient suppression performance. A simple model of GDT for personal simulation program with integrated circuit emphasis (PSpice) simulation, based on theoretical triac behavior, is proposed in this correspondence. The comparison between real measured characteristics and the proposed model results in a suitable approach for the overvoltage transient response without typical problems of numerical convergence.