With the aim to evaluate the therapeutic purgative efficacy of Cassia alata (Mezali-gyi or Pway-mezali) on healthy subjects, a study was conducted at the Clinical Research Unit (Traditional Medicine) Department of Medical Research, Lower Myanmar. The study was a controlled, complete cross-over single dose design using magnesium sulfate and phenolphthalein as positive standard. Ten clinically healthy volunteers (4 males and 6 females), 18 to 45 years old, were selected in this study. Pway-mezali fresh leaves (4 g) heated for few seconds for softening, magnesium sulfate (1 teaspoonful), phenolphthalein (0.8 g) and placebo (2 g) were administered weekly. Pway-mezali, magnesium sulfate and phenolpthalein showed significant (p<0.00005) purgative efficacy on frequency and volume when compared to placebo. Pway-mezali fresh leaves showed no significant different efficacy on frequency, volume and onset when compared to phenolphthalein. It was also found that the onset time of action of Pway-mezali and phenolpthalein is longer than magnesium sulfate due to the different mechanism of action. No side effects were observed in any of these subjects. It was concluded that Pway-mezali leaves showed purgative activity.