In an eight-subject two-way crossover study, 0.5-mg oral doses of digoxin were administered as two 0.25-mg tablets made by two different manufacturers. Treatment "B" yielded average peak plasma levels and areas under the curves that were 59% and 55%, respectively, of those attained following treatment "A". Two of the eight subjects also received the same dose in 5% dextrose both orally and by constant rate intravenous infusion during a one-hour period. Average peaks were 4.19, 3.76, 1.46, and 0.70 ng/ml following the intravenous infusion, solution orally, treatment A (tablet) orally, and treatment B (tablet) orally, respectively. Relative areas under the curves were 100%, 80.2%, 56.7%, and 30.7% for the treatments in the same order.