Abstract : From July 2011, a one-year study based on ethnographic methodology was carried out in “crack houses” in the neighborhood of Hochelaga-Maisonneuve in Montréal, Canada. The study aimed to explore the operational style of a specific indoor drug use setting and its impact on users’ risky sexual and drug use behaviors in a context of drug market change. A thematic analysis of observational and interview notes was conducted. This study stresses the importance to examine the role of environmental factors in relation to crack smoking’s health-related risks and to complement individual-based interventions with structural strategies. The study’s limitations are noted.