Autoantibodies are immunoglobulins that are directed against self tissues. Variable structural components of the cells or their products may be the targets. Production of a majority of autoantibodies is a physiological phenomenon, which does not have to lead to the disease. Autoantibodies that are associated with connective tissue diseases are produced in high levels, they are usually of high affinity and IgG isotype. Connective tissue diseases are characterized by a frequent presence of organ non-specific autoantibodies. Some of their properties can be used for clinical evaluation. The presence of the autoantibody may directly diagnose a specific connective tissue disease or support such a diagnosis. Some autoantibodies associate with typical clinical signs and symptoms, which sometimes form a specific subgroup with a different prognosis. Follow-up of the levels of autoantibodies is less significant, although they may occasionally help to assess the activity and contribute to a therapeutic decision. It is important to be aware of some technical limits that may affect the detection and interpretation of autoantibodies in the laboratory.