The relation between hydrophile Lipophile balance (HLB) and the parameters of a lattice fluid equation of state (Sanchez-Lacombe) are studied. The observed linear relation between the characteristic pressure (P *) and the HLB number, probably results from the fact that both parameters are connected to the cohesive energy density (CED). The relation between the HLB number and the number of lattice sites occupied by the alkylethoxylated surfactans in the lattice fluid model are also studied. (C) 1998 Elsevier Science B.V. All rights reserved.