Binding of divalent ions to zwitterionic phospholipids in monolayers and bilayers has been widely studied due to the obvious relevance of these systems to cell membranes and biological processes. Here we wish to investigate a synthetic surfactant system in which the charges on the zwitterionic headgroup are reversed. These surfactants are less environmentally toxic and less irritating than ionic surfactants so are of interest for encapsulation and use in materials where mildness is important eg personal care, therapeutics. The effect of binding of divalent ions on monolayer structure in this system is much less investigated than for the phospholipids, but will shed light on ion mediated polymer-surfactant interactions in this system and by analogy with the phospholipid-divalent cation system also help to understand ion binding in zwitterionic species in general.