We explore several aspects of Cycling Under the Influence (CUI) of alcohol and other drugs. CUI remains a relatively under researched topic, even though evidence suggests that it is a rising safety risk as both cycling mileage and alcohol consumption are increasing. We present the results of a quantitative survey designed to (i) assess the amplitude of the problem among Parisians and (ii) identify precursors for bicycle accident involvement and CUI practices. Our research provides evidence proving that CUI is indeed a common practice among Parisian cyclists (F(alcohol) = 46 % and F(drugs) = 10 %). Cyclists declare to be aware of related risks, but rarely adapt their drinking/cycling behavior to avoid them, even when they have previous accident involvement record. Shared vehicles’ users are more prone to CUI during night leisure outings when public transport is not available. Also, increased previous experience in cycling or in alcohol or drug consumption seems to make riders overconfident and therefore raise the probability of CUI.