Background A two-compound scalp formulation containing calcipotriol (50 μg/g) and betamethasone (0.5 mg/g; as dipropionate) (Xamiol, Taclonex Scalp) has been shown to be an effective and safe treatment for scalp psoriasis. Objective The aim of this study was to investigate the clinical efficacy of the two-compound scalp formulation after 1 week of treatment. Methods Pooled data from two large pivotal phase III trials with 2920 patients receiving once-daily treatment for up to 8 weeks with either the two-compound scalp formulation (n = 1108), betamethasone dipropionate (n = 1118), calcipotriol (n = 558), or the vehicle (n = 136) were analysed. Results The percentage of patients who had 'absent' or 'very mild' disease according to Investigator's Global Assessment after 1 week of treatment was significantly higher with the two-compound scalp formulation (30.6%) compared to betamethasone (24.1%; P <0.001), calcipotriol (10.0%; P <0.001) or vehicle (6.9%; P <0.001). Conclusion This data indicates that the two-compound scalp formulation demonstrated significant efficacy already after 1 week, with a faster onset of effect than either of the individual components in the same vehicle, in the treatment of scalp psoriasis.