Mice immunised with human epithelial mucin MUC1 coupled to oxidised mannan produce MUC1 specific MHC Class 1 restricted CD8(+) cytotoxic T cells and are completely protected from the development of MUC1(+) tumours; such therapy may be applicable to humans. In this light we describe pre-clinical studies in cynomolgus monkeys (Macaca fascicularis), to test the efficacy of mannan-MUC1 in higher primates. Monkey MUC1 genomic clones were isolated from a macaque library, peptides and fusion protein synthesised and mice and monkeys immunised with macaque MUC1-mannan. In mice CTL responses were induced (as has been found with human MUC1 mannan conjugates), but in contrast monkeys produced a humoral response, with no T cell proliferative, cytotoxic responses or CTLp found. In spite of the presence of anti-MUC1 auto-antibodies, there was no toxicity or induction of autoimmunity.