A method of determination of niobium in the form of Nb-Br-PADAP-tart- rate complex extracted with n-butyl alcohol is described. The interference of tantalum is eliminated by increasing the amounts of tartaric acid, and the color is stable for at least 40 hours. The detection limit is 0.01 µg/ml, and the C. V.% is 4 .9% for 10 determinations with sample containing 0.054% of Nb2O5.