Rheumatologists remain divided on whether they should introduce musculoskeletal ultrasound (MSUS) into their clinical practice. A central issue in the application of MSUS in clinical rheumatology is the need for proof of clinical relevance and improved patient care. There is now accumulating evidence that MSUS improves clinical diagnosis and intervention skills. High-resolution ultrasound is superior to clinical examination in the diagnosis and localization of joint and bursal effusion and synovitis. MSUS is the imaging modality of choice for the diagnosis of tendon pathology. MSUS is seven times more sensitive than plain radiography in the detection of rheumatoid erosions, allowing earlier diagnosis of progressive rheumatoid arthritis. Ligament, muscle, peripheral nerve and cartilage pathology can also be readily demonstrated by MSUS. There is exciting evidence that MSUS may potentially be used by rheumatologists to non-invasively diagnose and monitor not just joint and muscle disease but also nerve compression syndromes, scleroderma, vasculitis and Sjögren's syndrome. Joint aspiration and injection accuracy can be improved by MSUS, with initial evidence confirming improved efficacy. As the number of rheumatologists performing MSUS increases and the technical capabilities of MSUS improve, there is likely to be a growing number of proven clinical indications for the application of MSUS in rheumatology practice. This paper reviews the evidence for the application of MSUS in rheumatology.