A colorimetric, modified Kober reaction is applied to quantitative estimation of dehydroisoandrosterone on the basis of production of a unique, stable, blue color with a high peak maximum density at 600 m[mu]. Cooled aliquots within a range of 15-125 [mu]g. of dehydroisoandrosterone in 0.4 cc. of absolute alcohol are heated with 2 cc. of concd. H2SO4 for 2 min. in a boiling water bath, cooled in ice water for 25 min., diluted with 8 cc. of 13.2 N H2SO4, recooled in ice water, transferred to colorimeter tubes, and read in a photoelectric colorimeter (Evelyn) with a suitable filter (Rubicon 580) about 60 min. after final dilution. Evaluation is made against a calibration curve. According to Nielsen''s spectrophotometric technic (Acta. Endocrinol. 1: 121. 1948), the practical range for pure solns. is wider and readings are made with wave length 600 mu. Although the color is unique for dehydroisoandrosterone, androstenedione, testosterone (cis and trans), and desoxycorticosterone acetate produce a somewhat similar color with a high peak maximum in the same region, but unstable color and fluctuating fluorescence. Other similar steroids produce different colors with low density in the region of max. density for dehydroisoandrosterone, but the presence of appreciable amts. of androsterone depresses the color and androstenediol itself produces significant absorption. Specificity of color appears to be dependent on functional groups on C3 and C17 and unsaturation on C atoms 3,4, and 5 of the steroid molecules. The method is applicable to pure solns. and to suitably fractionated urinary extracts. Limitations and factors affecting the production and quantitative application of the color are discussed.