No single test allows an adequate measure of disease activity in multisystem diseases such as systemic lupus erythematosus (SLE). In order to evaluate the spectrum of manifestations of disease activity in SLE, investigators have developed numerous ad hoc scales which have not been tested for their validity or reliability. Three instruments have been extensively studied: the British Isles Lupus Activity Group instrument (BILAG), the SLE Disease Activity Index (SLEDAI), and the Systemic Lupus Activity Measure (SLAM). All three have been demonstrated to have convergent and construct validity when compared to the clinician's judgement. The summation of the number of criteria of the American Rheumatism Association (ARA) SLE criteria has been shown to be an inadequate measure of disease activity. Standardized measures of disease activity for SLE should enhance our ability to compare results from different centers in finer distinctions than dead or alive.