Single‐crystal fibers have been grown from high‐purity 1.5 wt&percent; Nd2O3 : Y2O3powder mixtures, and short lengths of the fiber in dielectric mirror resonators have been evaluated as lasers at both 1.07‐ and 1.35‐&mgr;m wavelength. The laser transition cross sections were approximately equal at the two wavelengths, and they were about two‐thirds the cross section of Nd : YAG at 1.31 &mgr;m. The fluorescence lifetime of the laser samples was 340 &mgr;sec. Loss in the material was approximately 3&percent; per cm. The absorption spectrum from 0.7 to 1.0 &mgr;m and fluorescence spectra for the 4F3/2→4I9/2, 4F3/2→4I11/2, and 4F3/2→4I13/2manifolds of Nd3+in Y2O3, taken with fiber samples, are reproduced in detail. The resultant energy levels are given. With a Kr laser operating at 0.7525 &mgr;m as the end pump, minimum observed laser threshold was 0.57 mW absorbed pump power for a 100‐&mgr;m‐diam 2.5‐mm‐long fiber operating cw in room‐temperature air at 1.07 &mgr;m. The lasers operated in one or two transverse modes and had active linewidths of approximately 2 A˚.