The effects of residual thiosulfate ions on the image stability in processed color paper were discussed to an accerelated test (70°C, 75% RH) and sunlight exposure. The amount of residual thiosulfate ions was determined as S₂O^2-₃ by methylene blue method. On the accerelated test, the presence of 0.1-1.0μg/cm² of S₂O^2-₃ resulted the remarkable effect to the fade of cyan dye and also increased the yellow stain. On sunlight exposure, the presence of the residual ion showed little effect to the image fading, and the fade of magenta dye was slightly retarded by much increase of residual thiosulfate ions. Color prints treated with a stabilizing bath at pH 3.6 after rinsing with water showed the relaxation for dark fading, light-induced fading and yellowing. It is desirable, therefore, to adopt the stabilizing bath treatment for protection of the fading.