A drug-facilitated sexual assault (DFSA) is a crime in which a person is sexually assaulted while under the influence of a psychoactive substance, significantly impairing its ability to give consent or defend oneself. Two types of DFSA are reported in the literature. In opportunistic DFSA, the victims willingly consumed a substance, and the offender takes advantage of its state of intoxication to commit a sexual abuse. In contrast, in proactive DFSA the perpetrator administers the substance to the victim for the purpose of committing the sexual abuse. The aim of this study was to assess the prevalence of both opportunistic and proactive DFSA in the registered cases of sexual violence by the “sexual assault centers” of Brussels, Ghent and Liege between 2017 and 2018. The data shows a strong implication of psychoactive substances in sexual violences with more than half of the registered cases mentioning the consumption or the effects of psychoactive substances, usually alcohol. Based on self-reported intoxication by the victims, 20-30 % of the cases might be classified as opportunistic DFSA, whereas the prevalence of proactive DFSA was estimated between 7 and 17%. High regular alcohol consumption was a significant risk factor for experiencing a sexual abuse under psychoactive substances. Whether opportunistic or proactive, DFSA were characterized by increased delays before contacting a sexual assault center and a reduced willingness to file a legal complaint. The results of the present study confirm the high prevalence of DFSA in Belgium, with alcohol being the most frequently involved substance. ; Étude du phénomène des agressions sexuelles facilitées par une substance en Belgique