IL-32 is a recently discovered cytokine that induces various proinflammatory cytokines (TNF-alpha, IL-1beta, IL-6) and chemokines in both human and mouse cells through the NF-kappaB and p38 MAPK inflammatory signal pathways. It is regulated robustly by other major proinflammatory cytokines and is crucial to inflammation and immune responses. Four of the IL-32 isoforms (alpha, beta, gamma, and delta) are the most representative IL-32 transcripts, and the gamma isoform of IL-32 is the most active, although all isoforms are biologically active. IL-32, a cytokine produced mainly by T, natural killer, and epithelial cells induces significant amounts of TNFalpha and MIP-2 and increases the production of both cytokines in a dose-dependent manner. IL-32 has been implicated in inflammatory disorders, Mycobacterium tuberculosis infections, inflammatory bowel disease, and influenza A virus infection, as well as in some autoimmune diseases, such as rheumatoid arthritis, ulcerative colitis, and in the human stomach cancer, human lung cancer, and breast cancer tissues. Thus, IL-32 expression might be valuable as a biomarker for cancer.