We have developed a pictorial multi-item scale, called P-SUS (Pictorial System Usability Scale), which aims to measure the perceived usability of mobile devices. The scale is based on the established verbal usability questionnaire SUS (System Usability Scale). A user-centred design process was employed to develop and refine its 10 pictorial items. The scale was tested in a first validation study (N=60) using student participants. Psychometric properties (convergent validity, criterion-related validity, sensitivity, and reliability), as well as the motivation to fill in the scale were assessed. The results indicated satisfactory convergent validity for about two-thirds of the items. Furthermore, strong correlations were obtained for the sum scores between verbal and pictorial SUS, and the pictorial scale was perceived as more motivating than the verbal questionnaire. The P-SUS represents a first attempt to provide a pictorial usability scale for the evaluation of (mobile) devices.