Twenty-two patients, all of whom reported never having been able to smell anything, were studied to determine the particular features that distinguish individuals with congenital anosmia. The clinical evaluation on these patients included a thorough medical and chemosensory history, physical examination, nasal endoscopy, chemosensory testing, olfactory biopsies, and imaging studies. There was no evidence to indicate that these patients ever had a sense of smell. The results of olfactory testing suggested that these patients had an inability to detect both olfactory and trigeminal odorants; however, many of the patients in the group seemed to have a slight ability to perceive at least some component of trigeminal odorants. The olfactory epithelium, if it was present at all on biopsy, was abnormal in appearance.