Recently it has been recognized that steady-state serum digoxin concentrations may increase or fall to ineffective levels when the glycoside is administered together with several antibiotics. Our study was designed to assess if serum digoxin levels may be modified by the concomitant use of a ticarcillin and clavulanic acid. The study was carried out in 15 hospitalized patients suffering from exacerbation of their chronic bronchitis without liver disease and renal failure. Serum digoxin levels were not significantly modified by the concomitant use of a ticarcillin and clavulanic acid, although peak digoxin serum concentrations were slightly lower. However, the average time to achieve the maximum concentration and area under the curve over 24 h did not change.