We have developed a high average power zig-zag slab laser based on conduction-cooling and a novel pumping geometry called edge-pumping. The edge-pumping geometry decouples the cooling and optical pumping interfaces, simplifying the laser head design. The advantages of this design include efficient pump absorption, uniform conductive-cooling, high brightness fiber-coupled laser diode pumping, and power scalability. We have demonstrated this new design in a Nd:YAG zig-zag slab laser which operates at 104 W of multimode power for 340 W of pump power with a 40% slope efficiency. TEM00 mode operation was demonstrated at 39.5 W for 250 W of pump power at a slope efficiency of 21%. Thermal lensing measurements indicate an effective focal length of < 0.5 m in both the zig-zag and the non-zig-zag planes for 340 W of pump power.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.