A process for preparing a linear, low-molecular-weight polyesterbased polyol having, (a) at least two hydroxyl groups, (b) low viscosity, (c) high solids content; comprising heat reacting at least one polyhydric alcohol having from 1 to 6 hydroxyl groups of which at least one is a primary hydroxyl group with at least one aliphatic saturated dicarboxylic acid or a lower alkyl ester thereof in a mol