An improvement of the oxidimetric determination of cobalt(II) with hexacyanoferrate(III) in ammoniacal solution, by means of a photometric end-point detection, is proposed. Amounts of cobalt down to 20 μg can be determined with fairly good accuracy and precision. Most common elements do not interfere. The interference of manganese(II) can be overcome using glycine or other amino acids as complexing agents instead of ammonia.