Abstract: Uroporphyrinogen decarboxylase (UROD) is a key regulatory enzyme that plays the important role in the metabolic flux through the branched biosynthetic pathway of chlorophylls, heme and siroheme in plants. The oppositifolious maize is special mutant that has high contents of chlorophylls in the leaves. In this study, maize UROD is purified to homogeneity from the young oppositifolious maize leaves by several purification procedures including ammonium sulphate fractionation, anion-exchange chromatography, gel filtration, hydroxylapatite absorption and reactive blue affinity chromatography. Its final specific activity for uroporphyrinogen III was 880 U/mg protein at pH 7.0 with a fold of 1060 and a yield of 8 %. The relative molecular weight of UROD holoenzyme was estimated about 60 kD using Sephacryl S-300 and that of UROD subunit was about 40 kD, as shown by SDS/PAGE. Determination of its pI and pH optimum revealed values 6.0 and 7.0 respectively. The purified UROD decreased 90 % activity incubating 12 min at 55 ℃. It was increased about seven-fold activity in the presence of the 100 mM concertration of 2-mercaptoethanol. Modification with pyridoxal 5-phosphate at a concentration of 5 mM caused a loss of about 40 % enzyme activity.