Methods of investigating horses with suspected shoulder lameness are described and discussed. The gait of shoulder lameness is characterised and compared with that of lower forelimb lameness. If lameness is slight, differentiation may be difficult, but if moderate, upper forelimb lameness usually results in shortening of the cranial phase of the stride and a low limb flight. Clinically, it may not be possible to differentiate between shoulder and elbow lameness without intra-articular anaesthesia. Practical aspects of intra-articular anaesthesia of the shoulder joint are reviewed. Synovial fluid must be retrieved to ensure that the needle is intra-articular. Up to 60 mins may elapse after injection of local anaesthetic before significant improvement occurs. Lameness is often improved rather than eliminated. A technique for standing radiography of the shoulder is described and the limitations of assessing a joint only by lateral projections are highlighted. There may be difficulties in positioning weanling foals and yearlings, resulting in superimposition of the shoulder joint, cervical and thoracic vertebra and ribs. It is concluded that a combination of a thorough clinical examination, faradism, local anaesthesia, synovial fluid analysis and radiography usually enables an accurate diagnosis to be reached.