A reanalysis of correspondence between electronic distribution of sulfonamides and their antibacterial activity is proposed. Correlation equations show that the rate limiting steps for sulfonamide action on E. coli cell-free system and whole cell system have similar dependence on the negative logarithm of the ionization constant. The existence of a "bilinear relationship" demonstrates that the whole class of compounds has a single mechanism of action and that permeability factors are unimportant in both biological processes.