Information about the prevalence of disorders of the chemical senses has been limited. In the late 1970s, the consensus among experts convened by the National Institutes of Health (NIH) was that more than 2 million adults in the United States had a disorder of smell or taste. A large, nonrandom survey conducted by the National Geographic Society in 1987 found that 1% of their 1.2 million respondents could not smell 3 or more of 6 odorants using a 'scratch and sniff' test. Age was an important factor, with a decline beginning in the second decade of life. No comparable data have been available for taste, although it has been suggested that the sense of taste remains more robust with age. The National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, began collaborating with the National Center for Health Statistics (NCHS) in 1993 to acquire information on the prevalence of smell/taste problems using the Disability Supplement to the National Health Interview Survey (NHIS). This survey was administered to approximately 42,000 randomly-selected households (representing about 80,000 adults over 18 years of age) in 1994. Adjusted national estimates derived from this survey showed a prevalence of 2.7 million (1.4%) U.S. adults with an olfactory problem. Also, 1.1 million (0.6%) adults reported a gustatory problem. When smell or taste problems were combined, 3.2 million (1.65%) adults indicated a chronic chemosensory problem. The prevalence rates increased exponentially with age. Almost 40% with a chemosensory problem (1.5 million) were 65 years of age or greater. In a multivariate analysis, the individual's overall health status, other sensory impairments, functional limitations (including difficulty standing or bending), depression, phobia, and several other health-related characteristics were associated with an increase in the rate of chemosensory disorders.