Responses to Chemical irritation can be obtained from the human respiratory mucosa in response to stimulation with gaseous CO₂; these negative mucosal potentials (NMPs) are thought to be summated receptor potentials from chemosensitive nociceptors. The present study aimed to investigate the relation of this response to both stimulus concentration and perceived intensity. A total of 29 healthy volunteers participated. Maximum negative amplitudes occurred 1.1 s after stimulus onset. The negativity exhibited a higher coefficient of correlation to intensity estimates of the painful sensations (r =.65) than to the stimulus concentration (r =.46); it appeared at the same time when the subjects' tracking of the painful sensations reached its maximum amplitude. These findings suggest that the NMP is suited for the investigation of peripheral nociceptive events in man.