Inappropriate or excessive medication use is a commonly observed problem among patients with chronic pain. Comparing patients' self-reported drug use with actual observed drug use, this study examines the incidence, nature and magnitude of drug utilization in a selected population of pain patients and evaluates the reliability of patient estimates of their own drug use. The data support the clinical observation that patients with chronic pain tend to underestimate their medication use. This tendency is greater for narcotic analgesics than for a variety of other medications taken for pain and is greater for women than men.