Electrical conductivity measurements for aqueous solutions of imipramine and clomipramine hydrochlorides have been carried out from (283 to 313) K. From these data, critical micelle concentrations (CMCs) have been obtained by application of the local polynomial regression method, which is based on a nonparametric estimation of the regression function. The method. is extremely flexible because it does not impose any parametric model on the subjacent structure of the data but rather allows the data to speak for themselves. The variation of the CMC with temperature was a second-order polynomial, with different trends for imipramine (convex) and clomipramine (concave). This distinct behavior was analyzed by the effects of dehydration of the headgroups and thermal solubility of molecules.