Studies have been made of effects encountered in the use of a gridded parallel‐plate ion chamber for energy measurements. These effects are: gas multiplication about the grid structure, capture of electrons by the grid, and variation of saturation characteristics between various gases and gas mixtures. Curves relating to these are presented for He, Ne, A, Kr, N2, He+3% CO2, A+3% CO2, and A+5% N2. It is found that the field conditions necessary to prevent electron capture by the grid may be correlated with electron lateral diffusion. Anomalies in connection with the behavior of argon‐carbon dioxide mixtures are pointed out, and several possible explanations for these are discussed.