Real-time quantitation of cytokine mRNA is a routine immunologic technique, especially fitting for use in those species for which monoclonal antibodies are not available. Quantitative gene expression assays were developed to assist in the immunologic assessment of three cetacean species including bottlenosed dolphins, Pacific white-sided dolphins and beluga whales. Nine cytokine genes (IL-2, -4, -10, -12, -13, -18, TNFalpha, TGFbeta and IFNgamma) and Cox-2 were selected for analysis. Most mitogen-induced mononuclear leukocyte responses were similar between the three cetacean species with either up- or down-regulation of cytokine genes. IL-10 expression was highly variable between species. No TH/1TH2 polarization was evident. Cytokine gene analysis has the potential to identify immune system perturbations induced by environmental insult as well as providing diagnostic tools for characterizing immune responses to environmental antigens and vaccines.