The purpose of the present work was to study the relationship between the physicochemical characteristics of different polyethylene glycol aqueous solutions and the kinetics of potassium chloride release from wax matrix samples containing polyethylene glycol derivatives. Potassium chloride was embedded into thermosoftening matrix material to produce a sustained-release dosage form. Potassium chloride release was measured by the rotating paddle method of USP 23 and the dissolution process was characterized by a modified Nernst equation. Physicochemical characteristics--surface tension, dynamic contact angle, viscosity--of the polyethylene glycol aqueous solutions were also determined. The results indicate that the adhesion tension of surfactant containing aqueous solutions has a decisive impact on the prediction of the potassium chloride release rate from wax matrices.