BACKGROUND: Psoriasis is a common, chronic, inflammatory skin disease with the majority of individuals having limited disease, treated with topical medication. However, special attributes of topical treatments like galenic/cosmetic properties or an inconvenient treatment schedule may result in low preference for topical treatments. Hence, there is strong medical need for a topical medication, which is highly efficacious, easy-to-use and preferred by both physicians and patients. OBJECTIVE: Blinded interim analysis with the purpose to assess efficacy of (both from the physician's and patient's perspective) and the patients' preference with a highly efficacious and easy-to-use fixed combination of calcipotriol/betamethasone dipropionate topical gel after 8 weeks of once daily treatment in a large patient population. METHODS: In this phase IV, international, multicentre, randomized, controlled, prospective, parallel group study, adult patients with active, mild to moderate psoriasis despite previous topical psoriasis treatment, i.e. unsuccessful in the 8 weeks preceding study participation, are followed over 64 weeks. During the first 8 weeks the patients apply their medication once a day followed by a 56-weeks maintenance period according to SmPC. Blinded interim analysis of all patients included demographics, Physician's Global Assessment, the novel Patient's self Global Assessment (PsGA) and Patient Preference Questionnaire (PPQ). RESULTS: 1795 patients were analysed. At week 8, 36.5% of the physicians rated the patients' psoriasis as clear/almost clear. Similarly, based on the patients' self-assessment, 34.2% had a clear/almost clear score of PsGA in week 8. Analysis of the PPQ showed that the vast majority of the patients judged their 8-week treatment to be preferable compared with their previous treatments. CONCLUSION: Results of this blinded interim analysis indicate that the fixed combination of calcipotriol/betamethasone dipropionate gel is highly efficacious and preferred by the majority of analysed patients.