The interactive effects of heat and mass transfer in evaporation of binary mixtures flowing as falling films on vertical surfaces was investigated. Evaporative heat-transfer coefficients were measured for aqueous mixtures of ethylene and propylene glycol, with boiling ranges up to 55-degrees-C. Tests were carried out at atmospheric pressure with heat fluxes ranging from 3,000 to 25,000 W/m2, and film Reynolds numbers ranging from 300 to 3,000. Results indicated that the heat-transfer coefficient for mixtures depends weakly on wall superheat and film Reynolds number, but strongly depends on mixture composition. Analysis of the results indicates that mass-transfer resistance in the liquid film causes significant elevation of the interface temperature, causing a reduction of the effective temperature driving force. A semiempirical model for correlation of the interactive heat- and mass-transfer phenomena is proposed.