This paper provides an up-to-date overview of the occurrence, diagnosis, risk factors, prognostic indicators and outcome of shoulder disorder (SD), and of the validity and reproducibility of diagnostic classifications and diagnostic imaging techniques for SD. Furthermore, the available evidence on the effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroid injections and physiotherapy for SD is summarized on the basis of randomized controlled trials with an acceptable quality of their methods. The annual incidence of SD is estimated at about 7%, its 1-year period prevalence at about 51% and its lifetime prevalence at about 10%. While approximately 50% of all patients with SD seek medical care, about 95% are treated in primary health care. Of all new episodes of SD presenting to primary care, approximately 50% seem to resolve within 6 months, while about 40% seem to persist for up to 12 months. Several prognostic indicators for a favourable or a poor outcome of SD have been identified, but a comprehensive prognostic model is not available. While evidence for the prognostic validity of popular diagnostic classifications of SD is lacking, their reproducibility has been shown to be poor. The accuracy and clinical usefulness of diagnostic imaging techniques appear to be sufficiently verified for SD in secondary care, while their clinical usefulness in primary care and prognostic validity are not. NSAIDs and steroid injections for SD have been shown to be effective within 6 weeks, but their effect on long-term outcome remains unclear. There is very limited evidence for the effectiveness in SD of physiotherapy, including exercise therapy, ultrasound, electrotherapy, laser, mobilization and manipulation.