A glycerol derivative or a salt thereof is provided and the derivative is represented by the following general formula (I): ##STR1## wherein n is an integer ranging from 1 to 3; R.sup.1 represents a hydrogen atom or a group: --P(O)(OR.sup.2)(OR.sup.3) wherein R.sup.2 represents a hydrogen atom or a protective group for the phosphoric acid residue and R.sup.3 represents a hydrogen atom, a protective group for the phosphoric acid residue or a hydrophilic group; provided that the phosphoric acid residue represented by R.sup.1 may be in the form of a salt wih a proper counter ion; and, in respect of stereochemistry of asymmetric carbon atoms present in the molecule, the derivative or salt may be either an optically active isomer or a racemic isomer.These compounds are excellent in biological compatibility, dispersibility and chemical stability and that they can provide membranes having high flowability and high barrier properties as compared with conventional phospholipids.