This paper reports on two prospective studies of ultrasound examination of the hip in 150 healthy subjects and 50 patients with hip joint diseases. The sagittal distance of the anterior recess of the hip was measured on the sonogram of the sagittal section. The normal value in adults, teenagers and children was 4.54 mm +/- 0.99 mm, 4.27 mm +/- 1.26 mm and 3.40 mm +/- 0.93 mm, respectively. Ultrasound examination of both hips in 50 patients with hip joint diseases showed that the sagittal distance of the anterior recess was significantly widened in the symptomatic side, and the mean value in the symptomatic side and normal side was 12.02 mm +/- 3.68 mm, and 4.12 mm +/- 1.15 mm, respectively. Ultrasound showed echo-free area in anterior recess in 42 hips, hypoecho and medium echo area in 8 hips. Of 50 patients undergoing plain radiography, 33 showed bony changes of the hip, and the remaining 17 no change whatever. The results obtained demonstrated that ultrasound can accurately detect effusion of the hip, what is more, it is easy to operate, inexpensive, noninvasive, convenient for follow-up and without radiation damage.