3,4-Methylenedioxymethamphetamine, or MDMA, is increasing in popularity in the United States as a drug of abuse. It has stimulant and empathogenic mood altering properties with the potential to affect psychomotor skills and impact driving. This report reviews the literature relating to the relevant psychomotor effects of the drug, the relationship between dose and blood concentrations, and studies and case reports on specific effects of the drug on driving. The latter reports include both laboratory driving simulator studies and anecdotal reports, and case series. We also report details of eighteen cases of apparent MDMA impaired driving, including six drivers whose blood tested positive for MDMA alone. Most subjects displayed muscle twitching and body tremors, dilated pupils, slow pupillary reaction to light, elevated pulse and blood pressure, lack of balance and coordination, and most were perspiring profusely. Five of the six subjects were given field sobriety tests (one leg stand, walk and turn test), and all five performed poorly. There was no clear correlation between the blood concentration of MDMA and the specific demeanor of the subject. These findings are consistent with other reports, and lead to the conclusion that MDMA use is not consistent with safe driving, and that impairment of various types may persist for a considerable time after last use.