Association characteristics of antidepressant drug Citalopram hydrobromide in water have been examined and its thermodynamic parameters have been calculated using tensiometery and conductometry.  The critical micelle concentration (cmc) was determined by surface tension measurement at 30°C and Surface activity was studied by measuring surface parameters i.e. surface pressure, ?, surface excess concentration, ?, area per molecule of drug and standard Gibbs free energy of adsorption, DG°ads. The electrical conductivity was measured as a function of concentration at various temperatures and cmc was calculated in the temperature range 20-50°C.  Thermodynamic parameters i.e. standard free energy of micellization, DG°m, standard enthalpy of micellization, DH°m and standard entropy of micellization, DS°m were calculated from cmc value using closed association model.