Ecstasy (3,4-methylenedioxymethamphetamine) is a popular recreational drug, a "designer drug", which has been developed from the basic structure in amphetamine. Ecstasy has now reached the illegal drug market in Denmark via the US, Great Britain and Sweden. The drug is related to a certain youth culture from which it is estimated that many drug abusers have been recruited. The desired effects of ecstasy, namely enhanced openness, awareness and empathy, have previously been used in various therapeutic connections. In later years the drug has led to abuse which, in connection with certain cultural behaviour patterns (for example in discotheques), can cause dangerous psychiatric as well as somatic effects. The undesirable psychiatric effects range from fear through depression to actual psychoses, and the somatic effects vary from symptoms of increased sympathetic activity to malignant hyperthermia, disseminated intravascular coagulation, rhabdomyolysis, renal failure, and lethal hepatotoxicity. The last mentioned symptoms occur in connection with prolonged physical activities such as exhausting dancing sessions. The article discusses the available treatments for conditions of abuse and stresses the need for prophylactic efforts in the form of information and awareness of the problem.