This correspondence describes the design and performance of a high-average-power longitudinal-flow Nd:POCl3liquid laser. In the long-pulse-mode of operation, 12-J pulses at 1.45-percent efficiency were obtained. At 30 pps, the laser produced 336 W of average power. Single 3-J pulses, 50 ns wide, were obtained at a repetition rate of 5 pps when the laser wasQswitched with two synchronized rotating prisms. This is the highestQ-switched energy reported for liquid lasers to date.