An electrostatographic single-pass multiple station (e.g. multi-colour) duplex printer is described for forming an image onto a web (12). The printer comprises at least three toner image-producing electrostatographic stations (A, B, C, D, A', B', C', D'). Each station has rotatable endless surface means in the form of a photoconductive drum (26) onto which a toner image can be formed. The printer also includes drive rollers (22a, 22b) for conveying the web (12) in succession past said stations (A, B, C, D, A', B', C', D'). Corona discharge devices transfer the toner image on each rotatable surface means (26) onto the web (12). The image-producing stations (A, B, C, D, A', B', C', D') are arranged in two sub-groups, the drum (26) of one sub-group forming a backing roller for the other sub-group, and vice-versa, thereby to enable simultaneous duplex printing.