The party environment is a natural habitat for research on MDMA use and its effects. Research shows that internationally the dance scene is associated with drugs, especially MDMA. This holds true in the Netherlands. The Netherlands is an important producer and distributor of MDMA and it is relatively easily available throughout the country. However, quantitative data on the motives ravers endorse to take MDMA is minimal and scarce. This study set out to describe patterns of MDMA use at different kinds of parties, to identify a set of motives for using the drug, and to test if party style and the endorsement of certain motives were associated with perceived positive and negative effects of the drug. Study participants consisted of 490 visitors of 3 different types of rave parties in the Netherlands, “club/mellow,” “trance/mainstream,” and “hardcore” during 2001 and 2002. Results indicated that partygoers were motivated primarily by the energetic and euphoric effects they expected from MDMA. The quantity of MDMA use was associated with hardcore and trance/mainstream party style with the motives of euphoria, sexiness, self-insight, and sociability. Motives are important predictors of positive and negative effects. Together, these findings on party cultures of MDMA use suggest that information on the possible negative (long-term) effects of MDMA use should particularly be directed at specific kinds of parties that cater to specialized audiences. Tables, references