Measurement of anti-DNA antibody activity has become a routine laboratory procedure of value in diagnosing and managing patients with systemic lupus erythematosus. However, there is no agreement as to the most suitable technique that should be employed. In this review, currently available assay procedures are critically evaluated with particular emphasis on accuracy, simplicity, reproducibility and ease of standardisation. The nitrocellulose filter technique appears to possess most of these qualities and is recommended as the standard assay for the measurement of anti-DNA activity in the clinical laboratory.