Cyclophosphamide (CYC) has long been considered a gold standard in inducing renal remission and preventing renal flares for patients with systemic lupus erythematosus (SLE). However, the rational use of CYC has not reached a consensus, such as the timing and length of treatment, the route of administration, and the ideal dosage. The objective of this study was to assess the efficacy and safety of short-interval lower-dose (SILD) intravenous (IV) CYC in the treatment of SLE. A total of 225 patients with lupus nephritis were randomly assigned to a 1-year trial, either the SILD group (12 fortnightly pulses at a fixed dose of 400 mg followed by 6 monthly pulses) or high-dose (HD) group (6 monthly pulses followed by two quarterly pulses at a dose of 0.5~1.0 g/m(2)). At 6 months of treatment, 28 % (30/107) of patients in the SILD group reached a complete remission (CR), and 51.4 % (55/107) were in partial remission (PR), as compared with 32.7 % (35/107) and 45.8 % (49/107) in the HD group, respectively. Serum albumin, 24-h urinary protein, and the scores of disease activity were significantly improved in both groups at 6 months and maintained at the end of clinical trial. However, the SILD group showed much less menstrual disturbances (11.5 %), gastrointestinal adverse effects (5.3 %), and leukopenia (9.7 %) than the HD group (28.6, 26.8, and 19.8 %, respectively) at the end of clinical trial. The efficacy of the short-interval lower-dose (SILD) IV CYC regimen in the treatment of lupus nephritis is equivalent to that of the high-dose (HD) regimen, whereas the incidence of adverse events is much lower in the SILD group.