Introduction - Homeless individuals, exposed to harsh weather conditions, face an increased risk of hypothermia due to alcoholism and underlying medical conditions. The objective of this article is to describe the characteristics of hypothermia cases detected in Paris during 2004 and to identify the associated risk factors. Method - A case-control study was conducted using intervention records completed by nurses from mobile teams, including demographic, clinical, and environmental indicators. In 2004, 107 cases of hypothermia were identified in 82 individuals, representing 7% of interventions. We matched 246 homeless controls based on the month of diagnosis. Results - The majority of diagnosed hypothermia cases (90%) were mild in severity; none were severe. Hypothermia cases were identified throughout the year, most frequently in November and December. In multivariate analysis, the risk of hypothermia was increased by heavy alcohol consumption (ORa=2.5; 95% CI [1.2–5.6]) and reduced mobility (ORa=2.4; 95% CI [1.1–5.4]). Discussion - The risk of hypothermia is significant in this subpopulation, and the number of cases detected represents a conservative estimate of reported cases in Paris in 2004, due to the lack of systematic case-finding by various community outreach teams. Training for various stakeholders in the detection and initial management of hypothermia cases would be essential to reduce the risk of morbidity and mortality. (R.A.)