This study was performed to investigate the effects of the common cold on olfactory function, which was assessed using chemosensory event-related potentials (CSERP, in response to both olfactory [H2S] and trigeminal [CO2] stimuli) and psychophysical measures (intensity ratings, odor discrimination, butanol threshold); nasal volume was assessed by means of acoustic rhinometry. The investigation was performed in 36 subjects (18 women, 18 men). After onset of the rhinitis (day 0) measurements mere performed on days 2, 4, 6 and 35, The cold produced a decrease of the volume of the anterior nasal cavity accompanied by an increase of mucus secretion, an increase of olfactory thresholds, a decrease of intensity ratings and a decrease of N1 CSERP amplitudes to olfactory and trigeminal stimuli. When mucus secretion of the contralateral nasal cavity was controlled with oxymetazoline, N1 amplitudes to olfactory stimuli were still affected by the cold as indicated by the significant increase of amplitudes as subjects recovered; this phenomenenon was not found for responses to trigeminal stimuli, This indicates that the common cold has a small effect on olfactory function which may be independent of nasal congestion.