Following the advent of molecular targeted drugs, a paradigm shift in treatment similar to that in rheumatoid arthritis has been expected in the treatment of systemic lupus erythematosus (SLE), but clinical trials for drugs that many specialists believed to be effective have failed repeatedly. The causes are not simple, but include the heterogeneity of SLE, inclusion criteria, lack of appropriate disease activity measures, and relapse criteria. This review outlines the disease activity indices used in SLE, discusses their advantages and disadvantages, and describes the ideal activity index.