Immunohistological characterisation of ovine rectal tissue has revealed the presence of lymphoid follicles, predominantly in the submucosa, that closely resemble those found in intestinal Peyer's patches (PPs). Distinct T (CD4+, CD8+, gammadelta-TCR+) and B (CD21+, CD45R+) lymphocyte staining patterns were observed within and around follicles of the rectal mucosa. In addition, IgA+ and IgE+ cells were also found at this tissue site, with both phenotypes commonly residing in the lamina propria. RT-PCR examination of the cytokines expressed in the rectal mucosal tissue revealed consistently high levels of TGFbeta and IL-8 mRNA, low levels of IL-2 mRNA and no detectable IL-4 mRNA. The presence of lymphoid follicles, IgA+ plasma cells and IgA-inducing cytokines in rectal tissue of sheep indicate that this may be a suitable route for delivering mucosal vaccines.