The cytokine TNFa plays an important role in the induction of inflammation e.g. in rheumatoid arthritis. Because TNF receptors are also expressed in dorsal root ganglia (DRG), we investigated whether the proportion of TNFR1 or TNFR2 receptor positive lumbar DRG-neurones changes during inflammation after induction of antigen-induced-arthritis (AIA) in the right knee joints of rats. DRG´s (L1-L5) from both sites were removed from normal rats and from rats at 0, 1 3, 7 and 21 (each n=5 rats) days after induction of AIA. The ganglia were fixed, embedded, cut into sections and incubated with an anti-TNFR1 or anti-TNFR2 antibody. In the control group 27,7 ± 10,7% neurones were TNFR1 and 57,7%± 9,4 % neurones were TNFR2 positive. The proportion did not change significantly during AIA. Double labelling experiments with an anti-TNRR1 antibody and IB4 indicates that about 1/3 of the TNFR1 positive neurones are IB4 positive. We conclude that both TNFR1 and TNFR2 are expressed in DRG neurones of the normal rat but neither in the acute nor in the chronic stage of AIA the proportion of labelled neurones was different from control.