Abstract: Immunocytochemical analysis of peripheral blood mononuclear cells was undertaken using a streptavidin biotin–horseradish peroxidase method to detect CD5 positive lymphocytes from the blood of several marsupial species. A monoclonal antibody raised to a conserved peptide sequence of the human CD5 antigen positively labelled lymphocytes in freshly isolated peripheral blood mononuclear cells of the tammar wallaby (Macropus eugenii), the long-footed potoroo (Potorous longipes), the long-nosed potoroo (Potorous tridactylus) and the rufous hare-wallaby (Lagorchestes hirsutus). A polyclonal anti-CD3 antibody also positively labelled circulating lymphocytes from the tammar wallaby. Whereas previous studies using flow cytometry reported labelling of T cells in koala lymphocyte preparations using a polyclonal anti-CD3 antibody, there have been no other reports of marsupial blood immunophenotyping. The current study extends the known applications of monoclonal anti-CD5 and polyclonal anti-CD3 antibodies to blood lymphocytes of small wallaby species using an immunocytochemical slide technique that is simple, can be processed within a day and requires no dedicated large equipment.