The aim of our study was to assess local anti-inflammatory effects of high dose immunoglobulin G (IgG) in rheumatoid arthritis (RA). Eleven patients with definite RA, having flare-up of knee joint synovitis, were included in the study. Six received an intra-articular injection of 1 g of IgG in 10 ml saline and five received an intra-articular injection of 10 ml physiological saline alone. The effect of the treatment was evaluated clinically and by magnetic resonance imaging using gadolinium contrast enhancement. In one of the six patients that received intra-articular IgG and one of the five patients that received physiologic saline a modest decrease of synovial hypertrophy was noted. None of the patients experienced clinical signs of increased joint inflammation as a consequence of the treatment procedures. The results of this pilot, double-blind, placebo-controlled study do not support local administration of IgG as an anti-inflammatory treatment in patients with RA.