Disclosed are antagonists of IL-17A and IL-17F. The antagonists are based on soluble IL-17RA and IL-17RC fusion proteins, including hybrid soluble receptors comprising portions of both IL-17RC and IL-17RA (“IL-17RC/IL-17RA”). Such antagonists serve to block, inhibit, reduce, antagonize or neutralize the activity of IL-17F, IL-17A, or both IL-17A and IL-17F. Also disclosed are methods of using such antagonists for treating disease, particularly inflammatory diseases mediated at least in part by IL-17A and/or IL-17F.