An observation on the accuracy of the titration method for ascorbic acid with 2,6-dichlorophenolindophenol adapted by the Department of Nutrition, Chinese Academy of Medical Sciences. The photometric method of and the paper chromatographic method of Robert et al. was made. The percentage error of the determination is -3.1-1.36% (above 18?g); -3.9-6.7%; and -6.1--18.4% (above 11.1?g) and also the percentage recovered of the added amount of asorbic acid is 95-99%; 95-109% (above 31?g) and 76.5-97.5% respectively.We have modified the developing reagent used by the paper chromatographic method and rendered it more sensitive.The photometric method of et. al. is found to be more adaptable than the other two methods, therefore further observations on the colorimetric method were made.1.The reproducibility of this method is comparatively good and a considerable amount of excess of 2,6-dichlorophenolindophenol (0.15 ml.) added at the end point has no influence on the results.2.The standard curves are not identical at different times of estimation so that parallel determination of optical density of the standerds and the sample should be made.3.The stability of the colour developed is much better than that obtained with Bessey's method.