A kinetic fluorimetric method is developed for the determination of microamounts of copper(II) on the basis of its catalytic activity on the hydrolysis of 2-hydroxybenzaldehyde azine. To monitor the reaction, the appearance rate of fluorescence in the hydrolysis reaction product, the 2-hydroxy benzaldehyde hydrazone (λexe= 355 nm., λem= 465 nm.), is measured. The determination of copper at the 100–500 ng/ml level suffers very few interferences. The mechanism of this catalyzed reaction is proposed.