Phospholipid monolayers of L-alpha-dipalmitoylphosphatidylcholine (DPPC) as insoluble monolayers, at the air-water interface and their dynamic behaviour as soluble adsorption layers at the chloroform-water interface have been studied using the axisymmetric drop shape analysis. Investigations on insoluble DPPC monolayers spread on the surface of a pendent water drop indicate the expected states and the well-known phase transitions of condensed and expanded films. The plateau of the isotherm in the coexistence region however was found to be less horizontal than obtained in Langmuir-Blodgett balance measurements. Measurements of dynamic interfacial tensions at the chloroform-water interface as functions of time and DPPC concentration provide information on the formation of soluble phospholipid layers. The adsorption isotherm obtained by extrapolating the dynamic interfacial tensions to infinite time using a diffusional transport model yields a minimum area per molecule equal to the value of the molecule at the transition from the coexisting region into the condensed phase.