Stimulated emission from a clearly defined quantum well transition has been observed from single quantum wells as thin as two monolayers (ML, 1 ML=2.83 A˚). These results are unexpected since previous experimental and theoretical work has indicated that if the well widthLzis smaller than the scattering path length of electrons or holes, carrier collection becomes inefficient and the quantum well cannot support stimulated emission. Laser thresholds of these separate confinement, single quantum well samples are quite low, despite the fact that these ultrathin quantum wells are undoped and do not have graded band‐gap confining layers. These unexpected results can be explained in terms of the spatial extent of the wave function rather than the well thickness.