A number of chemicals with the same odor quality (fruity, floral, herbaceous, putrid) were assayed for their potential to activate second messenger pathways in cilia preparations from rat olfactory epithelia using a rapid-quench flow procedure. It was found that compounds with similar odor do not all activate the same second messenger but rather induced the formation of either cyclic adenosine monophosphate or inositol triphosphate. Thus, alternative reaction cascades can be activated by chemicals with a similar odor quality.