OBJECTIVE: To describe the results of ultrasonographic examination in a series of patients with chronic wrist pain and to define the proportion of occult carpal ganglion in these patients. DESIGN: A retrospective study including 57 patients with wrist pain consecutively referred for sonographic examination. The inclusion criteria for this study were a history of wrist pain longer than 3 mos with no wrist trauma, and no palpable mass at the wrist. Ultrasound examination with a 10-MHz linear transducer was used to detect wrist pathology. A well-demarcated anechoic mass with posterior enhancement and without vascularity within the mass on sonography was defined as a ganglion cyst. RESULTS: Thirty-three of the 57 patients (58%) were diagnosed by sonographic examination as having a ganglion in the wrist joint. The size of the ganglion demonstrated on sonographic imaging ranged from 2 x 5 mm to 10 x 9 mm on a longitudinal scan of the wrist (with a mean of 4 x 7 mm.). Surgical excision was carried out in 12 patients who had ganglions diagnosed by sonographic examination; in all cases, the mucin content of the specimen was demonstrated. Eight patients underwent local aspiration followed by steroid injection under the guidance of ultrasound. The aspirated content was a jelly-like substance. In these 20 treated patients, symptoms of wrist pain improved after intervention. CONCLUSIONS: The prevalence of occult carpal ganglion is common in chronic wrist pain patients. High-resolution sonographic examination facilitates early detection of occult carpal ganglion.