Since 1918 quinidine has been used successfully in the treatment and prevention of various cardiac arrhythmias, particularly extrasystoles, paroxysmal tachycardia, atrial fibrillation, and flutter. Since the oral ingestion of quinidine derivatives reach a blood plasma peak relatively quickly and the concentration following a single dose falls rather rapidly,1-5it is necessary to administer not only multiple daily doses but frequently night doses to maintain an effective plasma level. In order to avoid multiple doses, attempts have been made at various times to administer a slower- and longer-acting preparation. Sampson et al. (1952),6in an effort to find a more slowly absorbed and longer-acting preparation of quinidine, used a delayed-absorptive-coated tablet of quinidine sulfate. They gave 0.8 gm. as a single dose to five patients. The maximum quinidine level, which ranged from 2.3 to 3.3 mg. per liter (average, 2.72 mg. per liter) was reached in 5 to 12