Spectrophotometric and spectrofluorometric titrations of two strongly aggregating dyes, 1,9-dimethylmethylene blue (DMMB) and acridine orange (AO), by three anionic biopolymers, chondroitin sulphate A, DNA and teichoic acid (TA), have been described. Though the three polymers differ in their dye binding efficiencies and TA is a weak chromotrope, the equivalent weights of the polymers can be estimated accurately by these methods using the two dyes. Results show DMMB to be the preferred dye for spectrophotometric titration. The titrations can be used to estimate the equivalent weights of anionic polymers, and also for the quantitative estimation of such polymers of known equivalent weights.