The efficiency of a YAG: Nd3+-laser and the influence of pump-power level and of spectral filtering the pump light was studied. The laser was pulsed high above threshold. Without filtering the pump light, the maximum laser emission was reached 30 μs before the maximum pump power. With filtered pump light, the efficiency is doubled and the laser emission roughly follows the pump power. Dynamic input-output characteristics show an efficiency minimum at the pump-power maximum.