The experimental subjects were older than the average general population, more educated and considerably experienced in drug use. They considered themselves to have benefited by their MDMA experience, with no evidence of harm. There were moderate, consistent biochemical, cardiovascular and neurobehavioral changes within normal limits that peaked between one and two hours following ingestion, returning to predrug levels within 24 hours. This experimental situation produced no observed or reported psychological or physiological damage, either during the 24-hour study period or during the three-month follow-up period. While the subjects are not typical of the general population, the findings support the general impression among knowledgeable professionals that MDMA is reasonably safe, produces positive mood changes in users, does not cause negative problems (if used sparingly and episodically) and is without evidence of abuse. Certainly, any drug that causes ataxia, elevates blood pressure and pulse is potentially unsafe. One can say little about safety when effects and side effects are studied for only 24 hours and then a blood cytology is obtained after three months. In this study, safety must exclude long-term toxicity. Not enough is known about MDMA's long-range effects other than information from random anecdotal evidence supplied by a few clinicians plus self-reports by unselected and unsupervised users. From the information presented here, one can only say that MDMA, at the doses tested, has remarkably consistent and predictable psychological effects that are transient and free of clinically apparent major toxicity. The experimental subjects believed that MDMA is both safe and beneficial, but there is insufficient evidence to accurately judge either the drug's potential harm or benefit.