A review, analysis and discussion on the derivation and measurement of electron scattering cross-sections of gases mostly used in environmental scanning electron microscopy is presented together with some previously unreported experimental material. There are significant differences in values published for cross-sections of such gases. Scanning the electron beam across a clean edge seems to be a most reliable technique to produce and measure beam profiles, from which the scattering cross-sections can be obtained with high accuracy and reliability. Results based on this method produce an excellent agreement with a theoretically derived value of scattering cross-section using an average factor of energy loss for all inelastic collisions. The discussion addresses the difficulties involved and provides alternative ways to reliably obtain cross-sections as a function of accelerating voltage in the range mostly used in environmental scanning electron microscopy.