This study examines the relationship between MMPI scales and functional limitation for the chronic illness populations of chronic low back pain, migraine headache, hypertension and diabetes. Average MMPI profiles for these groups approximate those of previous studies with the chronic low back group having the most disturbed profile and showing elevations especially on the Hs, Hy and D scales. Several kinds of analyses, however, demonstrate that, in general, the MMPI group differences can be accounted for by individual self-rated functional limitation. The data do not support attempts at defining a low back pain or chronic pain personality profile apart from the emotional disturbance associated with chronic limitation and disruption of activity.