OBJECTIVES: To identify the meaning of descriptors patients use to describe the quality and severity of their pain by mapping word clusters that patients identify as synonyms for the same pain sensation. METHODS: Subjects were recruited by web posting and telephone screening.  Those self-reporting active treatment for Migraine or Low Back Pain (LBP) were scheduled for in-person interviews using card sort exercises with 93 different pain descriptors to identify those each subject commonly used to describe the pain associated with their condition, and to identify pairs of descriptors that describe the same pain. Network maps that diagrammed patient identified equivalences between descriptors were created for each condition using Netdraw (Borgatti 2002) and then compared. RESULTS: Subjects ranged between 19 and 70 years (mean age of 41).  The majority (73%) was female, 65% were working full or part time, and 59% were Caucasian. Migraine patients identified more descriptive synonyms to describe their pain (10% of all identified synonym pairs) than the LBP group (6%). For the Migraine group, most words used synonymously formed a single large cluster of connections. For the LBP group two main clusters of descriptors emerged, differentiating low-intensity and high-intensity pain. Patients in both groups tended to identify STIFFNESS-TIGHT, ACHING-HURTING, RADIATING-SHOOTING and PULSATING-PULSING-THROBBING as synonymous. LBP patients also associated RADIATING with movement (SPREADING/PENETRATING) and thermal (HOT) descriptors, while Migraine patients tended to use it interchangeably with PIERCING. Migraine patients described TIGHT as equivalent with SQUEEZING/CRUSHING, while LBP patients associated it with PULLING/TENSION. For LBP patients, SPREADING was closely associated with PENETRATING/RADIATING/SHOOTING, while for Migraine patients it was linked closely to THROBBING/GNAWING/FLASHING. CONCLUSIONS: While some descriptors were used to convey a more consistent meaning across groups, other descriptors demonstrated condition-specific meaning. These findings emphasize the importance of context of use when using pain as a study endpoint.