Miscibility of 17 beta-estradiol in Eudragit(R) RS and norethindrone in Eudragit(R) RS either physical mixes or solid dispersions was determined by modulated temperature differential scanning calorimetry using three heating programs. Heating program I-E revealed the melting point depression of 17 beta-estradiol in Eudragit(R) RS as a function of composition, estimated by the Nishi-Wang equation. Heating program II-E disclosed a single glass transition temperature of the blends lying between those of 17 beta-estradiol and Eudragit(R) RS, described by the Kwei equation. Heating program I-N demonstrated the reduction of norethindrone melting point when the concentration of Eudragite(R) RS increased. The parameters determined by the Nishi-Wang and Kwei fits were consistent with the interactions between blend components. No difference in the miscibility and interactions between blend components was observed in the blends prepared by physical mixes and co-evaporation. (C) 2008 Elsevier B.V. All rights reserved.