The unstimulated random migration and the serum-induced chemokinesis of neutrophils obtained from the peripheral blood of patients with rheumatoid arthritis (n = 19) was not different from those of controls (n = 20). However, neutrophils obtained from the joint fluid of rheumatoid patients (n = 10) demonstrated a reduced serum-induced chemokinesis which was correlated with the amount of immune complexes present in the synovial fluid. The chemotactic response of peripheral blood neutrophils from subjects with rheumatoid arthritis taking aspirin (n =11) was increased while that of those rheumatoid subjects not taking aspirin (n = 8) was the same as controls. It is concluded that although there is no impairment of the in vitro migratory capacities of peripheral blood neutrophils obtained from patients with rheumatoid arthritis, neutrophils obtained from synovial fluids exhibit a marked defect in chemokinesis which may be related to the ingestion of immune complexes within the joint space.