Abstract: IL-1 delta polypeptides and polynucleotides and methods for producing such polypeptides by recombinant techniques are disclosed. Also disclosed are methods for utilizing IL-1 delta peptides are polynucleotides in the design of protocols for the treatment of chronic and acute inflammation, arthritis, septicemia, autoimmune diseases (e.g. inflammatory bowel disease, psoriasis), transplant rejection, graft versus host disease, infection, stroke, ischemia, acute respiratory disease syndrome, restenosis, brain injury, AIDS, bone diseases (e.g. osteoporosis), cancer (e.g. lymphoproliferative disorders), atherosclerosis, and Alzheimer's disease, among others, and diagnostic assays for such conditions.