The potential of 5-amino-orotic acid (AOA) for spectrophotometric determination of metal ions is explored. Only the reactions with copper(II), cobalt(II) and osmium(VIII) are sensitive and suitable for this purpose. Ternary complexes of copper(II) formed with AOA and ammonia or pyridine can also be used for photometric determination of the metal and given better sensitivity and selectivity than the binary complex. Optimum conditions for determination of all the three metal ions have been established.