[en] Extraction-photometric method for molybdenum determination in complex materials (technological solutions, ores and effluents) using alizarin blue solution in the mixture of equal volumes of ethyl acetate and tributyl phosphate as a reagent in the presence of ascorbic acid is suggested. Ascorbic acid is necessary for vanadium transformation to tetravalent state and elimination of iron interferenct. The molar coefficient of light absorption equals 2.0x10₄, obedience of complex solutions to the Beer's law within the limits of 1-25 μg Mo in 25 ml, reagent lambdasub(max) is 500 nm, complex lambdasub(max) - 560 nm. Relative standard deviation during the determination of 25 μg Mo (the number of determinations n=10) amounts to 0.020. Thousand-fold weight amounts of the following ions are permissible: Al₃⁺, Fe₂⁺, As₅⁺, Pb₂⁺, Zn₂⁺e Cu₂⁺ (in the presence of thiourea); V₄⁺ (after reduction by ascorbic acid) is permitted in three- thousand-fold weight amounts; Re₇⁺ - in two-hundredfold weight amounts