Using radioligand binding assays, histaminergic H1, serotoninergic, dopaminergic and Beta adrenergic receptors were studied in human normal and osteoarthritic cartilage. The four studied receptors were present in normal cartilage; serotoninergic, dopaminergic and Beta adrenergic receptors were significantly increased in osteoarthritic cartilage while histaminergic H1 receptors were significantly increased only in osteophytic cartilage. The results are consistent with a non specific activation of osteoarthritic chondrocytes.