The present invention concerns a method and an apparatus for automatic staining of at least one tissue sample accommodated on a slide by applying reagents. The system may include at least one slide provided in a slide rack, a fluid containment element, a slide holder, a vertical slide positioner to pivot the slides to a vertical position, and a slide immerser element to immerse the vertical slide into a fluid containment element or even a dip tank. By pivoting the slides from a horizontal to a vertical position, an automated method and apparatus for carrying out a pretreatment in an automated staining apparatus may be provided. The pivoting of slides may ensure an appropriate orientation of the slides for both the pretreatment and the staining processes.