In this study, a baseline design (A-B) with multiple behaviors was applied to assess the effectiveness of exposure plus response prevention (ERP) techniques for approaching a case of bowel obsession (BO) in a 19 year-old male. The aim of describing this single case was twofold: to report on a functional analysis of this mental disorder and to assess the degree of effectiveness after using such an approach. For the assessment, simultaneous monitoring included several target behaviours (e.g. waiting time before exposure, duration of exposure, distance from Hospital). The ERP approach was conducted in an inpatient setting and consisted of 21regular exposures plus response prevention sessions. Our results showed that an ERP procedure was effective in this BO patient and was helpful in reducing his anxiety and avoidance behaviors.