Abstract The potential response of a cadmium ion-selective electrode was examined in twelve metal buffer solutions. In the absence of ligands, Nernstian response down to 10 −6 mol dm −3 was obtained between pH 4 and 8. in metal buffer solutions much lower concentrations could be measured, depending on the ligand and pH. The stability constants were determined successfully for cadmium complexes with various ligands: acetic acid, ammonia, glycine, iminodiacetic acid, ethylenediamine- N,N′-diacetic acid, nitrilotriacetic acid, N-hydroxyethylethylenediamine- N,N′, N′-triacetic acid (H 3HEDTA), ethyleneglycol-bis(2-aminoethylether)- N,N,N′, N′-tetraacetic acid (H 4EGTA), 1,3-diaminopropan-2-ol- N,N,N′, N′-tetraacetic acid (H 4DPTA), 2,2′-bipyridine, and 1,10-phenanthroline. In the cases of H 3HEDTA, H 4EGTA, H 4DTPA, and H 4EDTA(ethylenediamine- N,N,N′, N′-tetraacetic acid), the ion-selective electrode behaved abnormally under certain conditions. Critical conditions for the normal response of the ion-selective electrode are discussed.