Immunoglobulin A (IgA) nephropathy is a worldwide disease that causes end-stage kidney disease (ESRD) in up to 15-20% of affected patients within 10 years from the apparent onset of disease and in up to 30-40% of individuals within 20 years from diagnosis. No specific treatment has been established and there is wide variation in current practice. This systematic review evaluates the use of immunosuppressive agents to treat patients with IgA nephropathy. The Cochrane Renal Group Specialized Register, Cochrane Controlled Trial Registry, MEDLINE, EMBASE and article reference lists were searched for randomized or quasi randomized trials. Two independent reviewers assessed studies for inclusion criteria (biopsy proven IgA nephropathy, randomized trial, use of immunosuppressive agents) and extracted data regarding the effects of immunosuppressive agents on ESRD, doubling of serum creatinine, glomerular filtration rate, urinary protein excretion and side-effects. Data were analysed with a random effects model. The published trials were few (13 trials, 623 patients) and were generally of poor quality. Compared with placebo, steroids were associated with a lower risk of progression to ESRD (six trials, 341 patients, RR 0.44, 95% CI 0.25-0.80) and lower end-of-trial proteinuria (six trials, 263 patients, weighted mean difference (WMD) -0.49 g/day, 95% CI -0.25 to -0.72). Treatment with alkylating agents significantly reduced end of treatment proteinuria (two trials, 122 patients, WMD -0.94, 95% CI -0.46 to -1.43). Although the optimal management of patients with IgA nephropathy remains uncertain because of limitations with the existing published data, immunosuppressive agents are a promising strategy and should be investigated further.