Both the theoretical and experimental results of the extension of a filament of viscoelastic material by surface forces are presented. The filament is horizontally supported on an inviscid substrate fluid and is drawn out by interfacial force effects. A momentum balance establishes the general shape of the viscoelastic filament geometry and 16 mm motion picture film provides specific data. The results establish that the flow is an unsteady extension and that the filament bulges and contracts due to the presence of inertial effects according to Coleman and Noll's 1962 prediction. Extensional viscosity is also discussed.