We report on a diode-laser-pumped cw Nd: YAG laser operating at a power level of 150 W. By using a transverse pump geometry, the radiation of 54 diode lasers with an output power of 10 W each is coupled into a Nd:YAG rod. In multimode operation, an optical slope efficiency of 32\% and an optical to optical efficiency of 29\% are obtained. In TEM00 operation, an output power of more than 30 W is realized with an optical to optical efficiency of 10\%.