Aims: These last years, pharmacists gained more and more importance in the clinical support of patients. However, few studies have explored the clinical outcomes of a pharmaceutical intervention on chronic patients. Methods: A randomized controlled study single blinded, evaluating the impact of a single pharmaceutical interview on hypertension, type 2 diabetes and hypercholesterolemia patients not reaching the therapeutic objectives despite a drug therapy. Patients in the intervention group were interviewed by a pharmacist who provided patient education on pathology management and advice on how to deal with the pathology on a daily basis, and identified any prescription problems. The primary outcome was the proportion of patients reaching the therapeutic objectives for blood pressure, glycated hemoglobin level and low-density lipoprotein cholesterol level at the three-month follow up consultation. Results: Seventy-three patients completed the study. In the control group, 33.3% patients reached the therapeutic objectives with the usual care versus 61.7% in the intervention group (p=0.015). The intervention was significantly more effective on patients with more than five different drugs prescribed (+16.7% vs +60.0%; p=0.005) and with a high education level (+29.4% vs +68.8%; p=0.024). A much lower rate of type 2 diabetes patients reached the therapeutic objectives whatever the group. Interestingly, the efficacy of the intervention did not depend on the number of chronic diseases or age after adjustment for the number of different drugs prescribed. Conclusions: There is a concrete clinical and public health impact of a single pharmaceutic interview, especially on polypharmacy patients with hypertension or hypercholesterolemia.