In a study of 3.8 million attendees to 249 raves over 12 years, researchers found that almost 27,897 people visited a first aid station, and more than a third (10,100) reported a substance-related problem. Of these, 515 required professional medical care, and 16 cases were life-threatening. Most (66.7%) substance-related problems were associated with ecstasy, alcohol, or both. People using GHB most often required professional medical care, although the authors found no evidence for life-threatening, acute effects of the drug. The study was conducted based on data from raves in the Netherlands between 1997 and 2008 and was led by Jan Krul of Educare Groningen in the Netherlands. It is reported in the online journal PLoS ONE on Dec. 28.