Abstract: Ahighly sensitive spectrophotometric method has been developed for the determination of Mo(Ⅵ) by means of heating oxidized hemaloxyin and ascorbic acid in a boiling water bath. The conditions of the colour development in the system of molybdenum (Ⅵ)-oxidized hematoxylin-ascorbic acid were studied. The results obtained indicate that the highest sensitivity attained is associated with the commercial reagent labeled "hematoxylin" and with the preparation of oxidized hematoxylin solution. The coloured product showing maximum absorption at 450-460 nm obeys Beer's law in the range from 1 to 30 ng of Mo (Ⅵ) in 10 ml solution. The apparent molar absorptivity has been found out to be 2.14×10⁷. The effect of various cations and anions on the system was investigated and it was observed that oxidized hemetoxylin-ascorbic acid is a selective reagent for Mo (Ⅵ) in the presence of NH₄ Fat proper concentration. However, more than 100 ng Mo (Ⅵ) in the 10 ml solution interferes with the determination. The method is simple and convenient and has been used for the direct determination of Mo(Ⅵ) in surface water and in urine with satisfactory results.