Abstract: Pyridoxylidene, one of the vitamin B_6 components,may react with amino acids to form various kinds of Schiff-bases. The Schiff-base was labelled with ~(99m)Tc using stannous chloride as reductant.This note reports in detail the efficiency of labelling under several conditions such as the pH of the solution, relative quantities of reductant, and the reaction time either in boiling water or at room temperature. The purpose of this note is to give an optimum conditions of labelling and to evaluate the clinical application of the labelled Schiff-base.