A cholecystokinin (CCK) test was performed on 13 female patients who were thought to be having attacks of gallbladder pain and in whom at least one cholecystogram had been normal. In 10 of these patients the CCK test was performed during the course of a repeat cholecystogram in order to assess the effect of CCK on gallbladder contraction. There was no constant relationship between a positive test and gallbladder contraction as measured radiographically. Cholecystectomy was undertaken in 9 patients and of these, 4 had been CCK positive, 4 had been CCK negative and 1 had reacted equivocally. None of the CCK positive patients had stones at operation, whereas 2 of the CCK negative patients had one or two small stones. In this small series cholecystectomy relieved both the CCK negative and CCK positive patients of pain with equal frequency. It is concluded that a negative CCK test by no means excludes the presence of symptomatic gallstones in patients with X-ray negative gallbladder pain.