During 'I love techno' (edition 2001), an indoor rave party attended by 37 000 people, data about medical problems (especially drug-related problems) were collected. To place these data in a wider perspective, a similar registration was done during 'De Nacht', a traditional New Year's Eve dance party held at the same location and attended by 12 000 people. Furthermore, a prospective study on the time course of the level of consciousness (Glasgow Coma Score) and blood concentrations of illicit drugs, especially gamma-hydroxybutyrate was set up. The results revealed that during 'I love techno' the incidence of medical problems was high (66.5/10 000 attendees), but not higher than during 'De Nacht' (70.0/10 000 attendees). At 'I love techno', however, mainly illicit drugs were used, more frequently leading to severe drug-related medical problems. The observations in patients with a drug-related medical problem who had taken gamma-hydroxybutyrate showed that for a given level of consciousness the gamma-hydroxybutyrate concentrations may show important differences, that the transition from coma (Glasgow Coma Score < or =7) to full recovery (Glasgow Coma Score 15) takes only 30-60 min (and only a small decrease in gamma-hydroxybutyrate concentrations), and that the time it takes before a comatose patient reaches the above-mentioned 'transition area' may be a few hours.