Abstract We present the cases of two patients (19- and 40-year-old women) with systemic lupus erythematosus (SLE) who showed marked elevation of C-reactive protein (CRP). In both patients, pleural and/or peritoneal effusions were caused by lupus serositis. Methylprednisolone pulse therapy was effective in improving the serositis and normalizing CRP. Although it is generally considered that the CRP response is relatively weak in lupus patients, these cases suggest that a strong CRP response can occur in a subset of SLE.