In patients with rheumatic and, especially, connective tissue diseases many organ systems apart from the joints may be involved, such as the skin, muscles, salivary glands, nerves, kidneys and blood vessels. Biopsies of these tissues may help in establishing a diagnosis, in assessing the extent and severity of the disease and in monitoring the success of therapy. In this chapter, indications for biopsy, technical procedures, potential results and possible complications are described. The emphasis is on when a biopsy is indicated, how the patient is prepared, how the biopsy is performed, what results can be expected from the biopsy and what are the possible sequelae. For full details of the histology of e.g. a renal biopsy in a lupus patient, the reader is referred to the relevant textbooks.