The stability constants of complexes of N-[(tris-hydroxymethyl)methyl]glycine (Tricine) with the transition metal ions Co2+, Ni2+, Cu2+, and Zn2+ were studied potentiometrically in the presence of (0.02, 0.05, 0.10, and 0.15) mol dm(-3) KNO3; in the presence of (60, 65, and 75) vol % acetone, 75 vol % ethanol, and 75 vol % dioxane at 0.05 mol dm(-3) KNO3 at 25 degreesC; and at (5, 15, 25, 35, 45) degreesC in the presence of 0.1 mol dm(-3) KNO3. The thermodynamic stability constants for tricine and for tricine + M(II) [where M(II) = Co2+, Ni2+, Cu2+, and Zn2+) have been obtained from the measurements.