Twenty-seven chemicals all containing the >CC< group have been tested for their potential sensory irritation properties to the upper respiratory tract when administered in an aerosol form to mice. An analytical model for the data is suggested for comparison of the activity of these compounds, and the essential molecular features for sensory irritant activity in these compounds are delineated. Correlation between the biological and chemical reactivity data suggests that these compounds initiate the sensory irritation reaction by associating with SH groups of a receptor molecule on the free nerve endings of the afferent trigeminal which are located at the surface of the nasal mucosa.