Laser emission has been generated in 15ND3 by pumping at 860.4 cm-1. Strong laser action has been observed at 123 cm-1, 109 cm-1 and, with up to 10 millijoules extracted, at 628.1 cm -1. Spectroscopic analysis indicates that the pumping arises from, and the 628.1-cm-1 emission terminates on, the same rotational state. Analysis of the time histories of the three laser emissions as well as studies of laser output energies indicates that 15.9-micron output arises from a 4-wave type process. This system, in addition, clarifies the interpretation of earlier studies of CO2-laser-pumped ammonia lasers.