PURPOSE: The objective of this study was to evaluate the findings of ultrasonography (US) in patients withis-chial bursitis. MATERIALS AND METHODS: Our study included 27 patients (mean age 62 years) who underwent US fora painful mass or tenderness in the buttock area. In six of these 27, serous fluid was obtained by needleaspiration, and in five cases, bursal excision permitted histologic confirmation. The other sixteen patients werefollowed up for one or two months with only NSAID medication; all showed some improvement or remission of symptoms. Using a 5-10 MHz linear array probe, US examination was performed while the patient was lying facedown. US images were analyzed with regard to location and size of the lesions, thickness of cyst wall, thepres-ence of internal septa or mural nodules, echogenicity of the cyst wall, fluid content, internal septa,compressibility by a probe, and Doppler signals within the cyst wall. RESULTS: In all 27 patients, ischialbursitis was located superficially to ischial tuberosity. Lesion size(maximum diameter) was 1.5-7(mean 3.8)cm, andthe cyst wall was 0.2-0.8cm thick. Internal septa and mural nodules were seen in 12 cases (44%) and 13 cases(48%), respectively. The cyst wall was identifiable in 21 cases (78%), appearing as a single layer with lowechogenicity (n=10) or with high echogenicity (n=1); it also appeared as two (n=6) or three (n=4) layers ofdifferent echogenicities. When internal septa were present, fluid within the cyst was low echoic in 59% of cases,high echoic in 30%, and of mixed echogenicity (so-called compartmentalization) in 15%. In all cases, the cystbecame deformed, when compressed by a probe. In all patients who underwent doppler examination, some vascularitywas found within the cyst wall. CONCLUSION: US helped to detect ischial bursitis; US findings were thin-walled cystic lesion located superficially to ischial tuberosity, with or without internal septa and mural nodules, andeasy compressibility.