Confluent cultures of osteoarthritic and rheumatoid human synovial cells were treated with human recombinant tumor necrosis factor alpha (TNF-α) The cytokine increased uptake of 2-deoxy-D-[1-3H]glucose (2-DOG) in a time- and concentrations-dependent manner. In synovial cells obtained from osteoarthritic patients (OA cells), the stimulation of 2-DOG uptake occurred 3 hours following addition of TNF-α (1 ng/ml) and was maximal by 24 hours Rheumatoid synovial cells (RA cells) appeared less sensitive to the cytokine: 2-DOG uptake stimulation was only significant after 6 hours of incubation. In both OA and RA cells, the effect was protein synthesis-dependent, and was not secondary to prostaglandin E2 synthesis or cell growth. Interteukin-1β was more efficient than TNF-α for 2-DOG uptake stimulation The two cytokines seemed to act in an additive manner.