Abstract: The application of Craven's color reaction of p-benzoquinones with ethylcyanoacetate to menadione was studied systematically. A simple and accurate colorimetric method for the determination of menadione sodium bisulfite was developed. The procedure is proposed as follows. To 10 ml 55% alcoholic solution, containing 0.5--0.8mg of menadione sodium bisulfite, add 0.5ml of an alcoholic solution of ethyl-cyanoacetate (1: 20) and 2.5 ml of strong solution of ammonia. A blue color is produced. Dilute with alcohol to exactly 25 ml after 5 minutes and mix well. Allow the mixture to stand for 30 minutes, read the optical density at 598 mμ in a spectrophotometer or in a photoelectric colorimeter with a yellow filter, usiug distilled water as blank. This method is suitable for quantitative determination of menadione sodium bisulfite in injections and tablets with an accuracy of +1%.