Imipramine-HCl reacts with ammonium vanadate in the presence of HCl to give a green colour having maximum absorbance at 400-410 nm. The reaction is selective for imipramine-HCl with 0.001 mg/ml as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's law from 0.001 mg to 0.05 mg/ml of imipramine-HCl and the relative standard deviation is 1.1%. The quantitative assessment of the tolerable amount of other drugs is also studied. The method has been applied to pure drugs as well as to commercial preparations and is precise and reproducible.