It was shown previously that at low concentrations of sodium dodecylsulfate (SDS) and methylisobutylcarbinol (MIBC), hydrophobic force plays an important role in the stability of foam films (Wang and Yoon, 2005, 2006). In the present work, effects of nonionic surfactants (n-alkyl polyoxyethy1ene homologues) on the stability of foam films have been studied, with particular emphasis on the role of hydrophobic force. The magnitudes of the hydrophobic forces in foam films were determined from the equilibrium film thicknesses and the film thinning kinetics measured using the thin film pressure balance (TFPB) technique. The results show that single foam films thin much faster than predicted by the DLVO theory due to the presence of hydrophobic force. In general, hydrophobic force decreases with increasing concentration of a non-ionic surfactant. It was found also that hydrophobic force decreases with increasing chain length of the n-alkyl group and with decreasing chain length of the EO groups.