A group of young people who had indicated that they regularly visit parties of the house-party type, using MDMA and other drugs including alcohol, were tested in a driving simulator, early in the morning shortly after having visited a party, under the influence of MDMA and possibly various other drugs. The participants were first tested before the party under the influence of MDMA alone and also tested sober, i.e. on a control night at a comparable time. The latter is reported elsewhere in this volume. After the party, at their wish, they were picked up at the party, brought to the test facility again and tested. In the simulator they again completed a test ride that included driving in an urban environment and on a motorway. Performance was assessed in terms of lateral control (swerving), longitudinal control (speed headway) and decision making (response to braking manoeuvres of leading cars, gap acceptance while crossing a junction). In addition to performance participants self-reports performance and experienced effects were collected. Results indicate that basic vehicle control is only moderately affected. There are, however, indications that more so than under the influence of MDMA alone, after the party subjects accept higher levels of risk.