Methods are described for the long-term monitoring of visual changes which can occur in color photographs kept in the dark or exposed to light on display. A photographic color densitometer is used to measure changes in stain levels and in the integral red, green, and blue optical densities of the images, which consist of cyan, magenta, and yellow dyes or pigments. Procedures are given for making polyester print overlay sheets to record precise measurement locations. A separate fading monitor, which can be used to distinguish between deterioration caused by exposure to light and that which occurs in dark storage, is described. A system of long-term densitometer calibration using refrigerated photographic gray scales and color scales is outlined. The types of visual and physical changes which can occur with common types of color photographs are described. Quantitative limits for color print image deterioration which take into account stain formation, color balance changes, and losses in highand low-density portions of the image are suggested. See also 16-949, and 18-1827.