With a long experience in evaluating public health measures in the fields of HIV and drug addiction at national level, the Evaluation and Expertise in Public Health sector (CEESAN, Unisanté, Switzerland) has also been monitoring the situation in the canton of Vaud for more than twenty years. In this article, we present two instruments developed for epidemiological monitoring purposes : the « Pointage annuel du profil des usager·ère·s des structures à bas-seuil d'accès » (PAPU, annual measure of users of low-threshold facilities' profile) and the online platform for opioid agonist treatments. The data collected through these two instruments provide information on the main characteristics of precarious drug users in the canton and help to guide public policy in this field.