Abstract The thermodynamics of partitioning of some structurally related sulfonamides have been determined in 1‐octanol–aqueous buffer and liposome systems. The partition coefficients were approximately tenfold higher in liposomes compared with 1‐octanol. The enthalpies of transfer from aqueous media to organic systems were positive in liposomes but negative or positive in 1‐octanol, whereas the entropies of transfer were positive in almost all cases. Copyright © 2002 John Wiley & Sons, Ltd.