['Raves may be considered recreational settings in which drug use and health risks related to polydrug use are higher than in others. Harm reduction behaviors implemented by ravers are of particular relevance in reducing such risks. This study analyzes harm reduction behaviors and their relationship to raver polysubstance use patterns.', 'Cross-sectional study of 248 ravers recruited at underground raves in Andalusia (Spain). A questionnaire was developed to collect information about their sociodemographics, drug use, and harm reduction behaviors.', 'The results show that ravers employ harm reduction behaviors for minimizing drug-related harm. Nevertheless, only a small minority of the participants frequently employed harm reduction behavior for polysubstance use as well. Ravers identified as high polysubstance users protected themselves significantly less than those identified as low polysubstance users.'] Does harm reduction behaviors among young polysubstance users at rave?