This paper describes the design principles of multistage molecular evaporators with a wiped film which are used for gentle distillation of low-volatility blends of thermolabile materials. The conditions of distillation in an evaporator with a convex evaporation surface are discussed, along with problems relating to the function of the segmented wiper in the formation of the retarded liquid film and the functional principles of closing elements in a multistage evaporator with a single evaporating cylinder and of the built-in entrainment separator in the distillation space, which is designed to retain splashing spray. A TMO 65 three-stage molecular evaporator is described, with an evaporating cylinder having a diameter of 65 mm and a total evaporating area of 0.19 m2. This pilot-plant evaporator can be used in the small-capacity production of specialty chemicals or in technological research as a verification unit for establishing data necessary for the operation of large evaporators. These possible applications are documented by the results obtained on fractionation of various important materials. Fractional distillation of crude monoacylglycerols (M) containing 35 to 55% M afforded concentrates containing over 90% M, at yields of 78 - 95% M in the product fraction. Fractionation of oligomers of higher alpha-olefins gave distillate cuts with high contents of the respective n-mer, suitable for use as synthetic lubricating oils. Fractionation of polyalkylaromatic residue from the production of monoalkylbenzenes produced a distillate fraction with excellent electrical insulation properties. Finally, purification of technical diane-bis-glycidyl ether yielded over 75% of a product fraction which was found suitable for production of insulating material for electrical equipment operating at voltages of 6 to 15 kV.