The aim of the study was to investigate whether there are changes of the nociceptive system in patients with chronic inflammatory joint pain. A pain model was used which is based on the recording of cortical chemo-somatosensory event-related potentials (CSSERP) after nociceptive stimulation of the nasal mucosa with gaseous carbon dioxide (CO2). Twenty-five patients with rheumatoid arthritis (RA) were compared to healthy controls matched for age and gender. Responses to both different intensities of painful stimuli and constant intensities of series of 4 stimuli were analysed. When testing increasing COP concentrations ratings and CSSERP amplitudes increased for both patients and controls. However, when repetitive stimulation was performed with an interval of 2s CSSERP amplitudes NI were significantly greater in RA patients. It is hypothesized that chronic inflammatory joint pain changes nociceptive processing in terms of generalized changes of the nociceptive system which may amplify chronic pain. (C) 2001 Harcourt Publishers Ltd.