Fatty esters of oligoesters of a dicarboxylic acid and a polyol retaining at least one free hydroxyl group, particularly of the formula (I): R1-[OR2O-C(O)-R3-(O)C-]m-R4 (I), where R1 is H, a monocarboxylic acid group, or R6O-[C(O)-R3-(O)C]-; R2s are residues of polyols having at least one substituent free hydroxyl; R3s are hydrocarbylene; R4 is -OH, -OM where M is a salt forming metal, amine or ammonium, -OR6, or -OR2O-R7; R5 is C7 to C21 hydrocarbyl; R6 is C8 to C22 hydrocarbyl; R7 is H, or -C(O)R5; and m is 1 to 20; provided that at least one of R1 and R4 is or includes a C8 to C22 group, are surfactants. A range of surfactant properties can be obtained by varying the molecules within these ranges. Especially where R2 is derived from a higher polyol e.g. sorbitol, R3 is C2 to C6, and the fatty terminal group is C8 to C14, the products can be highly water soluble and effective oil in water emulsifiers.