Spectroscopic properties and acid-base equilibrium of hydroxyanthraquinone dyes have been studied in nonionic, cationic, and anionic micellar media as well as in other solvents, and it has been shown that the relative position of dye in micelle depends on the polarity of dye and nature of micelle. The shift of pK(a) value in nonionic micelle, pK(a)(i), compared to that in water, pK(a)(W), has been explained considering the shift of the relative position of the dye during deprotonation, associated with medium effect. Surface potentials, psi, for charged micelles at different bulk ionic strengths are calculated for different dyes, and it is noted that the influence of the bulk ionic strength on acid-base equilibrium of charged micelle bound dye depends on the relative position of the dye in the micelles. A simplified form of the pseudophase ion exchange model has been found suitable for quantitative interpretation of the change in apparent pK(a) values of the dyes with the change in the bulk ionic strength. This model has been utilized to calculate the intrinsic micellar pK(a), pK(a)(m), for different dyes. Comparison of these pK(a)(m) values with pK(a)(i) gives an idea about the average polarity of location of the dyes in micelles.