THE spectral behaviour of the Nd-glass laser has recently attracted much attention. Normally the output of the Nd-glass laser consists of a broad band of wavelengths (approximately 50 A wide) composed of hundreds of lines centred about 1.06µ (see Fig. 1A). This structure has been described in detail by Snitzer1. Time-resolved spectra1,2 and investigations of the pumping energy dependence of the output band-width3 all may be interpreted on the basis of inhomogeneous behaviour of the Nd+3 emission. The purpose of this communication is to report the efficient generation of a single narrow spectral line from a giant pulsed Nd+3 glass laser by passive Q-spoiling.