1 The time-course of quinidine plasma concentrations and selected kinetic parameters were studied in healthy male volunteers given single oral doses of four different quinidine formulations. Comparison was made with quinidine sulphate in a rapidly dissolving form. 2 Plasma half-lives did not significantly differ among treatments. 3 Quinidine polygalacturonate appears to be equivalent to quinidine sulphate in respect to both the absorption and elimination kinetics. When both quinidine bisulphate (Kinidin Durules) and quinidine arabogalactansulphate (Longacor) were administered plasma levels peaked significantly later than after quinidine sulphate. However, while the former seems to be absorbed to the same extent as quinidine sulphate, the latter exhibits lower bioavailability in respect to all other preparations.