A potential energy hypersurface for the adiabatic process C2H5*⇄H + C2H4 is derived. The potential energy at configurations corresponding to C2H5* is calculated using the STO-3G self-consistent field method. The C2H4 region is formulated from available semi-empirical information. The continuous potential energy surface is conceived as an interpolation between these arrangements. The lowest energy reaction path and general surface features are fitted to a general analytical form for use in dynamical calculations.