Mental disorders may result in severe precariousness of housing, with a worsening of the disorders, inappropriate hospitalizations, homelessness, substance abuse or even suicide. The « housing first » model offers direct access to housing with the support of a mobile psychiatric team, which bypasses the usual steps hospital - fostered home - independent housing. The goal of this article is to describe a « housing first » pilot project conducted in Lausanne. Demographics, clinical and services' use data were collected from participants 12 months before and after the integration into the program. 16 people have been integrated into housing. The average length (from 81 to 15 days) and the average number of psychiatric hospitalizations (from 1.31 to 0.44) declined significantly for 30%-60% less direct costs as compared to fostered homes. However, several obstacles remain to be overcome in order to continue this program.