Gray-scale ultrasound images of the shoulders of 6 rhesus monkeys were obtained before and after fluid instillation to assess the ability of ultrasound to diagnose joint disorders. The normal bony landmarks and muscular structures were shown. After the fluid was introduced, fluid collections were identified in the axillary pouch and subscapular bursa. Ultrasound is a promising new method of detecting intra-articular effusions of the shoulder.