Micellization of an amphiphilic phenothiazine drug promethazine hydrochloride (PMT) in presence of conventional (CTAB and TTAB) as well as gemini (16-s-16 and 14-s-14, s = 4-6) cationic surfactants has been studied conductometrically at different temperatures. Critical micelle concentration values (cmc and cmc(id)) indicate mixed micelle formation among the two components. Micellar mole fractions of surfactants (X-1, X-1(M) and X-1(id)) show greater contribution of surfactants. Interaction parameter, beta, suggests attractive interactions in the mixed systems. The thermodynamic parameters suggest dehydration of hydrophobic part of the drug at higher temperatures. (C) 2010 Elsevier Inc. All rights reserved.