A recent criticism of the Nottingham Health Profile (NHP) claimed it was an insensitive instrument for use in population surveys, because its modal response was zero, and domains measured by the instrument are insufficiently distinct. It is argued here that the NHP was designed specifically to uncover the chronically ill in populations and, further, research undertaken here indicates that the instrument is sufficiently sensitive to be successful in permitting variations within and between illness groups to be determined. However, the domains of mobility and pain, as measured by the instrument, are found to be confounded.