At a therapeutic level, infection by parasitic worms is controlled by the use of a range of anthelmintic drugs. However, increasing resistance to anthelmintic drugs indicates a need to develop alternative strategies to control helminth infections. The immune response to many helminth parasites results in a Th2 type (T helper 2) response. This response may be broadly characterized by activation of CD4+ Th2 cells with increased levels of Th2 cytokines, including interleukin (IL)-4, IL-5, IL-9 and IL-13. This type of response is thought to have developed largely to control pathogen invasion at mucosal sites and supports the protective response to helminth infections. In the mouse, IL-33 has been shown to play a role in the induction and effector phases of type 2 immune responses and has shown to play important role in mediating the effector response to parasitic infections, however, little is know about the role of this cytokine in the response to worm infections in the pig, a livestock animal particularly susceptible to helminth infections. With this in mind, we have identified porcine IL-33 by designing primers to Genbank published porcine IL-33 sequences. Porcine IL-33 was amplified from porcine alveolar macrophage cDNA and is 75% homologous to human IL-33 at the nucleotide level and 65% homologous at amino acid level. Moreover, the sequence also exhibits high level homology with other cloned mammalian IL-33s. The production of poIL-33 in a recombinant form will allow the assessment of the Th2 stimulating therapeutic potential for this cytokine and its role in helminth infections in pigs.