Khellin is a crystalline extract of a crude drug which has long been used in Egypt for the treatment of ureteral colic.1The pure crystals were independently isolated in 1930 by Fantl and Salem2and by Samaan.3Further studies of its chemical structure were made by Spaeth and Gruber4in 1941. Animal experiments later demonstrated that khellin is a coronary dilator with an action greater than that of aminophylline but not as great as that of amyl nitrite.5Khellin's duration of action is prolonged and it is relatively nontoxic and free from undesirable circulatory side-effects. These results prompted Anrep and his workers to use it clinically in patients with angina pectoris.5They found that the daily oral administration of khellin to 250 patients with mild to severe angina resulted in the complete cessation or a significant reduction in frequency and intensity of attacks in