Standard acidity constants, K-a(DMSO) (HA), expressed as pK(a)(DMSO) (HA) values, and anionic homoconjugation constants, K-AHA-(DMSO), (in the form of lg K-AHA-(DMSO) values) have been determined for 11 substituted phenol-phenolate systems in a polar protophilic aprotic solvent, dimethyl sulfoxide (DMSO) with a potentiometric titration. A linear relationship has been determined between lg K-AHA-(DMSO) and pK(a)(DMSO) (HA). The tendency towards anionic homoconjugation in these systems increases with increasing pK(a)(DMSO) (HA) that is with declining phenol acidity. The pK(a)(DMSO) (HA) are correlated with both pK(a)(W) (HA) in water and other polar non-aqeous solvents. (C) 2003 Elsevier Ltd. All rights reserved.