An investigation of the range-energy properties of fission fragments was undertaken by measuring range-ionization with the electron collection method. In order that these data could be converted to range-energy data, a theoretical investigation of the energy/ionization ratio was undertaken;The range-ionization data for light and heavy fragments in nitrogen and helium all gave the same curve. Light and heavy fragments in argon gave the same range-ionization curve, which differed from the nitrogen and helium curve. This difference was partially due to high electron diffusion in argon. Errors of electronic differentiation tended to reduce the possible difference between curves of heavy and light fragments;Simultaneous range-ionization data for both fragments of a pair were obtained from a double ionization chamber. The relatively few data obtained agreed with expectations;The following conclusions are made as a result of these investigations: (1) A reasonable interpretation of the results of the energy-ionization study is that the energy/ionization ratio for electronic collisions w e is constant, but about 1.9 Mev of light fragment energy and 3.4 Mev of heavy fragment energy lost in nuclear collisions does not appear as ionization. (2) Effects of electron diffusion and ion pair recombination lower the quality of the range-ionization data obtained by the electron collection method. Diffusion appreciably effects the argon data. Recombination makes the signal/noise ratio with nitrogen undesirably low and with hydrogen and carbon dioxide prohibitively low. The use of helium seems to be a compromise; neither recombination nor diffusion are objectionable. (3) The electron collection method is not well suited for distinguishing between the nearly alike range-ionization curves of heavy and light fragments. (4) The data indicated that the range-ionization curves for helium and nitrogen are the same, but this curve differs from the curve for argon. (5) The data from a double ionization chamber provide significant information on fission fragments only when they are in large quantity.