Clinical trials of pain are notoriously difficult and inefficient in demonstrating efficacy even for known efficacious treatments. Determining the appropriate pain phenotype to study can be problematic. Recent work has identified the extend of widespread pain as an important factor in the likelihood of response to therapy, but has not been tested in clinical trials. Using data from three previously published negative studies of the treatment of interstitial cystitis/ bladder pain with data on the extent of widespread pain, we examined the response of patients to different therapies base on the amount of pain beyond the pelvis. Participants with predominately local but not widespread pain responded to therapy targeting local symptoms. Participants with widespread and local pain responded to therapy targeting widespread pain. Differentiating patients with and without widespread pain phenotypes may be a key feature of designing future pain clinical trials to demonstrate treatments that are effective versus not.