This paper presents a mathematical model of a pulse-pumped Nd:YAG laser. The performance of cw-pumped systems has been described by Koechner in terms of the input power and output power. The operation of Q-switched systems has been modeled by Wagner and Lengyel. To the author's knowledge, no adequate model of the pulse-pumped laser exists. The two mentioned models are examined and aspects of each combined to produce a model of the pulse-pumped laser that allows its performance to be predicted from the mirrors-only resonator to the Q-switched system. The model applies equally well to a diode-pumped laser.