Capacity factors were determined for 20 disperse and solvent dyes by a high performance liquid chromatographic method using methanol/water and a C-18 reverse-phase column. Regression equations are given that establish relationships among capacity factors, water solubilities and octanol/water partition coefficients. The method is easy to apply to commercial dyes with resulting estimations that are accurate to better than one order of magnitude. Possible sources of error are discussed and suggested as implicit in the method when applied to dyes. The regressions are also used to estimate the octanol/water partition coefficients and solubilities for 14 other disperse dyes and for indigo, none of which have been measured previously. The estimated values for all of the dyes correspond to calculated sediment/water partition coefficients and bioconcentration factors, ranging from about 2.3 to 8.5 and from 2 to 7 log units, respectively. (Copyright (c) 1991 Elsevier Science Publishers Ltd, England.)