Patients with low back pain (LBP; N = 102), fibromyalgia (FM; N = 100), and headache (HA; N = 100) were asked to describe their pain in their own words, and the words and phrases they used were then classified into 7 global domains (eg, Pain Quality, Pain Magnitude) and as many specific subdomains as needed to capture all of the ideas expressed (eg, under Pain Quality, subdomains such as sharp, achy, and throbbing). Fifteen pain quality subdomains were identified as most common. Nine of these demonstrated significant between-group differences in frequency. For example, patients with FM described their pain as achy more often than patients with LBP or HA; patients with HA described their pain as more throbbing than patients with LBP or FM; and patients with LBP described their pain as more shooting than patients with FM or HA. With the 15 pain quality subdomains representing the universe of most important pain qualities to assess, only 2 of 8 descriptive measures of pain quality were determined to have content validity. The findings are generally consistent with a study that used similar procedures in other patient samples to identify the most common words patients use to describe pain, supporting their generalizability. The findings also support the use of pain quality measures for discriminating between chronic pain conditions. Finally, the findings have important implications for evaluating and modifying pain quality measures as needed.