Coherent emission has been generated by two‐dimensional arrays of SIS Josephson junctions and detected in a junction coupled to the array through a dc‐blocking capacitor. The detector junction exhibits Shapiro steps at frequencies corresponding to the voltage across single array junctions and ranging from 60 to 210 GHz. The maximum power coupled to the detector junction occurs at 150 GHz and is estimated to be 0.9 &mgr;W, based on simulations of the detector circuit. Possible mechanisms for coherent emission from two‐dimensional arrays are discussed.