The properties of insoluble monolayers and Langmuir-Blodgett multilayers of novel dicarboxylic acids are reported. Surface pressure-area per molecule isotherms and monolayer stabilities (at fixed pressure) have been measured as a function of subphase pH for four materials, differing in the structure of the chain linked to the carboxylic acid groups. The composition, with respect to ionisation, of multilayers deposited on germanium substrates has been determined using infrared spectroscopy, and it is found that the pH at which monolayers are maximally stable is close to that for which multilayers are half ionised. The differences in surface ionisation behaviour between the various acid compounds are discussed in relation to the ionisation of a monocarboxylic acid and ionisation of short chain acids in bulk. The possibility of headgroup staggering is suggested.