A study of single-dose digoxin kinetics was performed in 6 young and 7 elderly patients. The rate of absorption, determined by the time to peak concentration after an oral dose, was more rapid in the younger group. The extent of absorption, as measured by comparison of the area under the plasma concentration/time curve after oral and intravenous administration, was similar in both groups. Mean plasma half-life was longer and individual values were more variable in the elderly patients. The absolute apparent volume of distribution was reduced in the older patients and correlated inversely with age. When corrected for weight, however, the difference in the apparent volume of distribution did not approach significance. Both absolute and weight-corrected values for plasma clearance of digoxin were reduced in the elderly subjects.