Inhibition of bleaching by sensitizing dyes adsorbed to developed silver was studied. Change of zeta potentials and the heat of adsorptions to developed silver were measured for various types of cyanine dyes. The bleaching rate of developed silver adsorbed by the dyes was determined. On bleaching with ammonium ferric salt of ethylenediaminetetraacetic acid, adsorption of the dyes inhibited the bleach to a great extent, depending upon negative charge and heat of adsorption of them. Consequently, inhibition is presumably attributed to adsorption of dyes to silver and increase in negative charge barrier. For stronger bleaching agent such as ferric chloride, however, bleach was hardly affected with dyes.