The relationship between the pressure‐dependent electron attachment rate constants which have been observed in 1‐C3F6and in several perfluoroalkanes and the uniform field breakdown strengths (E/N)limin these gases is discussed. Also discussed are the various types of synergistic behavior in (E/N)limwhich have been observed in binary dielectric gas mixtures. For the latter, a new mechanism is outlined which explains the synergism observed in several gas mixtures where the (E/N)limvalues of the mixtures are greater than those of the individual gas constituents, which we callpositivesynergism. Model calculations are presented which support this mechanism and can be used to explain the pressure‐dependent synergistic effects which have been reported in 1‐C3F6/SF6and other gas mixtures. Experimentally observed ion–molecule reaction processes for several gases are discussed which support the proposed mechanism. Based on this mechanism, we outline several conditions which must be fulfilled in order to observepositivesynergistic behavior in dielectric gas mixtures.