The behavior of a cadmium selective electrode made of, CdS-Ag₂S in the presence of compleging agents is discussed. For systematic observation, eight typical oompleg- ing agents, namely EDTA, EDTA, NTA, Trien, nitrate, tartrate, acetate and NHa have been selected. In the presence of added cadmium(Ⅱ),the response of the electrode decreases when pH is above 8-9, showing the hydrolysis of cadmium ion. In the absenco of addod oadmium(Ⅱ),a much higher value was found egporimentally for oho concentration df cadmium than that calculated from eq.(1).