1. A spectrophotometric method is discussed which permits quantitative analysis of colored substances present in mixtures. 2. Special attention is given to the analysis of mixtures of two dyes which are being used in a series of studies on vital staining. 3. It is shown that the method can be applied to quantitative analysis of mixtures of naturally occurring animal pigments or to mixtures of these with various other colored substances. 4. Certain limitations of the method and certain necessary precautions are discussed.