The slow degradation of GaAlAs LEDs in accelerated aging has been studied by the capacitance spectroscopy method. We observed a drastic increase in the density of two deep levels A and B in the active layer during a homogeneous degradation of the LEDs. The deep levels A and B are hole traps with activation energies of 0.43 eV and 0.76 eV, respectively, and they are commonly observed in LPE GaAlAs. An increase in the cutoff frequency of the LEDs (-1.5 dB point in light output) during aging was also observed. An explicit correlation between the density of these levels and the cutoff frequency was shown with the homogeneous degradation of the LEDs, which shows a possibility that the deep levels in the active region contribute to the slow degradation of GaAlAs LEDs. The degraded LEDs were examined in the transmission electron microscope. No images of defect structures over 100 Å dia. were found in any part of the active region.