Our improved approach combining the renormalized Fermi-gas model (RGM) with the use of an average collective potential energy surface (PES) has been used to estimate the energy release in prompt fission phenomena from fission of excited nuclei. The role of excess excitation ΔUI on top of the fission barrier, under several assumed constraints, is discussed. The partition of ΔUI into the conjugate prompt fragments has been calculated from a simple RGM saturation condition. The practical limits of ΔUI have been discussed from the viewpoint of the statistical model of nuclear reactions. The number of evaporated neutrons from the prompt fragments νF has been estimated from LeCouteur and Lang's approximation using Wing and Varley's neutron binding-energy tables. Fairly satisfactory agreement for the number νF has been obtained with the experimental work on fission of Th230 by 25.7- and 29.5- MeV He4 ions and of Ra226 by 13.0-MeV protons. A linear relationship of the average number of prompt neutrons ν̄ with ΔUI is predicted from our model. © 1971 The American Physical Society.