The photoconductivity of cadmium sulfide can be sensitized for the wave length longer than the fundamental absorption of the host crystal by the dyes adsorbed on the surface. Although many kind of cyanine dyes were used to sensitize thephotoconductivity of cadmium sulfide, the following special features of interrest are pointed out. (1) Some dyes show the sensitizing character of J-band by the presence of J-aggregate on the surface of CdS, which is similar to the case of silver halides. (2) The time response of photoconductivity of cadmium sulfide is fast when cadmium sulfide is sensitized by some dyes.