Spectral changes in the spontaneous emission from stripe‐geometry GaAs double‐heterostructure junction lasers have been observed to occur during their noncatastrophic degradation under continuous operation at room temperature. As a result of prolonged continuous operation, the optical wavelength for maximum external spontaneous emission increases significantly as the degradation progresses. In some lasers the wavelength shift has been observed to occur only in the emission from one mirror of the laser with the spectral emission from the other mirror remaining unchanged. The observed changes in rapidly degrading lasers are interpreted in terms of the formation of a localized region of high optical absorption within the active region. The absorbing region is identified by visual observation through thensubstrate of a degraded laser as a volume in which little or no spontaneous emission occurs near the lasing wavelength. In addition, the absorption is shown to be dispersive, exhibiting a sharply increasing absorption edge with increasing energy.