Microelectrode voltammetry was employed to gain information on the n-octanol/water partition ratio of phenothiazine dyes. The data were obtained as a function of pH and dye concentration in aqueous solutions. All the dyes present hydrophobic behavior at pH above 7.0. The analysis of the results shows not only the formation of neutral species in alkaline solution but the association of cationic form of these dyes with OH- play important roles in the partitioning of molecules from aqueous solution to n-octanol. (C) 2014 Elsevier Ltd. All rights reserved.