A highly sensitive, rapid and simple square-wave procedure for the determination of Mn(II) has been developed. Mn(II) in triethanolamine (0.1 M) and KOH (0.15 M) gives a well-defined, reversible peak at -0.456V vs Ag/AgCl. The calibration curve is linear in the concentration range of 0-100 µg/ml. The minimum concentration that can be determined is found to be 40ng/ml (s.d. = 4.2%). Effect of various ions, which commonly occur with Mn9II0, has also been studied. The procedure has been applied for the determination of Mn(II) in low alloy steel samples.