Ephedrin hydrochloride reacts with sodium diphenyl amino sulfonate and potassium periodate to give a yellowish red colour having maximum absorbance at 470 nm. The reaction is selective for ephedrin with 1 μg/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 to 0.3 mg/ml of ephedrin. The standard deviation does not exceed 0.050 mg/ml. The method is successfully applied to pure and pharmaceutical preparations of ephedrin. The quantitative assessment of tolerable amounts of other drugs is also studied.