OBJECTIVES: Patient’s perception regarding their treatment has a real interest in healthcare, especially in chronic disease. The Percepolis study aims to describe patient’s preference regarding their ESA treatment.  METHODS: This is a 6-month multicenter prospective Non-Interventional Study conducted by 111 French nephrologists in 2011. Eligible patients were patients not on dialysis, ESA naïve or not at baseline. The primary endpoint was the relative importance according by the patient preference to different characteristics of ESA treatments. Patients had to complete a questionnaire at baseline and around 6-month. Questionnaire was developed using a CBC analysis method with the following hypothesis: 1) 7 ESA characteristics; 2) from 2 to 3 levels per characteristics; 3) each possible answer includes 1 level for 2 characteristics; 4) 2 choices per question; 5) and 6) 7 questions per CBC questionnaire. The number of combinations between all characteristics and levels was 288, and 20 questionnaires have been generated in order to mix all possible treatment characteristics and levels. Patients only had to answer one questionnaire and a randomization has been used to obtain equal number of respondents for each questionnaire. CBC analysis was planned and performed for subgroup of patients already receiving ESA or not. RESULTS: A total of 790 patients were included, 609 questionnaires were analyzed at baseline. Fifty-five percent of patients were already treated by ESA, among them the most important characteristic was the planned frequency of administration for 31%, followed by the importance of the treatment efficacy for 20%, the pain at injection site for 11%. But when asking a direct question to patient on which characteristic was the most important, 82% of them answered treatment efficacy, 5% for pain at injection site and frequency of injection. Similar results were found for ESA naïve patients. CONCLUSIONS: The CBC analysis revealed that frequency of injections is underestimated by patients and should be taken into account by physicians when choosing an ESA treatment.