The interaction forces in microscopic foam films stabilized with the soluble zwitterionic phospholipid lauroyl lysophosphatidylethanolamine have been studied by measuring the thickness/electrolyte concentration and disjoining pressure/thickness isotherms in the presence of Na+ and Ca2+ in solution. Electrostatic long-range repulsive interactions leading to formation of thick silver-colored films are found to be operative at low NaCl concentrations. The determined diffuse electric layer potentials (phi(o)) for the two studied surfactant concentrations (C-s) are low, 35 and 20 mV, the lower value corresponding to the higher C-s. These potential values are considered negative in conformity with the previously advanced assumption of the important role of OH- ions for formation of negative charge at the film interfaces. The obtained results agree well with previous results obtained for foam films formed from nonionic surfactant and phospholipid solutions showing that in the case of 1-1 valent electrolyte the film behavior is determined by the zwitterionic character of the phospholipid head group and not by its structure. The results obtained at low CaCl2 concentrations show lower phi(o)-values due to Ca2+ ions binding at the initially negative film interfaces. The increased positive charging leads to a charge reversal at the film interfaces at concentrations higher than 0.02 mol dm(-3) CaCl2 causing a Newton to common black film transition. Further increase in CaCl2 concentration leads to decrease in film thickness until again Newton films are obtained. The comparison of these results with previous data obtained for foam films stabilized with lysophosphatidylcholine shows the importance of the phospholipid head group structure for the Ca2+ binding which determines the electrostatic interactions in foam films stabilized with neutral phospholipids with CaCl2 added.