Recombinant human interleukin-1 alpha (rhIL-1 alpha) and recombinant human interleukin 1 beta (rhIL-1 beta) stimulated the time- and concentration-dependent release of glycosaminoglycan (GAG) from bovine nasal cartilage explants. Maximum GAG release occurred during six to eight days of cartilage exposure to either species of rhIL-1; and rhIL-1 alpha was consistently more potent than rhIL-1 beta. In addition to inducing cartilage matrix resorption, rhIL-1 alpha and rhIL-1 beta also inhibited the incorporation of [35SO4]sulfate into cartilage, which is a reflection of the suppression of GAG synthesis. IL-1 had no capacity to stimulate GAG relase from or inhibit GAG synthesis by dead cartilage. Cycloheximide, an inhibitor of protein synthesis, and 1, 10-phenanthroline, a metalloproteinase inhibitor, suppressed rhIL-1-stimulated cartilage matrix resorption. Polyclonal antisera to rhIL-1 alpha and rhIL-1 beta specifically neutralized the respective cytokines.