Responses from the middle turbinate elicited by olfactory and trigeminal stimuli were studied using the intrinsic optical signal (IOS) recording technique. Nasal cavity was illuminated by 617 nm light. Olfactory (H2S) or trigeminal (CO2) stimuli of 5-s duration were presented using a computer-controlled olfactometer; IOS responses were captured by a special camera. Averages across five individual IOS recordings were analyzed. When the nasal cavity was exposed to H2S, a significant change of the IOS was found; responses to CO2 were even more pronounced. The present results argue for the idea that the IOS is an indicator of intranasal chemosensory activation.