In the present communication, an attempt has been made to develop an empirical relationship between HLB and equilibrium surface tension values of surfactants having characteristics of intermediate class between anionic and non-ionic type, viz. ethanolamine derivatives of long chain alkyl ester of phosphoric acid. It requires a new methodology to evaluate their HLB value experimentally following the Becher's method of studying its behavior in aqueous solution as all other existing formulae except Davies' theoretical approach are not applicable to them. The validity of the proposed formula log HLB = 0.12 γeqm -2.65, to calculate HLB over a wide range of surfactants varying ionic nature, viz. ethanolamine derivatives of alkyl sulphate, alkyl esters and ethoxylates of different polarities, has been found to be acceptable. © 2009 Indian Society for Surface Science and Technology.