It is demonstrated that conditioned media of articular chondrocytes cultured with Bacilli Calmette-Guérin are capable of activating macrophages. This activation reaches different levels and is expressed both by different cell survival and enhanced synthesis of glycosaminoglycans that remain cell-associated (exp. group III) or are secreted (exp. group II). The reason of these variances is unknown. - A protein factor is supposed to be present in variable concentration or activity. Interleukin-1 could not be correlated with the results.