Background: The majority of children who present with their first episode of nephrotic syndrome achieve remission with corticosteroid therapy. Children who fail to respond may be treated with immunosuppressive agents including calcineurin inhibitors (cyclosporin or tacrolimus) and with non-immunosuppressive agents such as angiotensin-converting enzyme inhibitors (ACEi). Optimal combinations of these agents with the least toxicity remain to be determined. This is an update of a review first published in 2004 and updated in 2006 and 2010. Objectives: To evaluate the benefits and harms of different interventions used in children with idiopathic nephrotic syndrome, who do not achieve remission following four weeks or more of daily corticosteroid therapy. Search methods: We searched Cochrane Kidney and Transplant's Specialised Register (up to 2 March 2016) through contact with the Information Specialist using search terms relevant to this review. Selection criteria: RCTs and quasi-RCTs were included if they compared different immunosuppressive agents or non-immunosuppressive agents with placebo, prednisone or other agent given orally or parenterally in children aged three months to 18 years with SRNS. Data collection and analysis: Two authors independently searched the literature, determined study eligibility, assessed risk of bias and extracted data. For dichotomous outcomes, results were expressed as risk ratios (RR) and 95% confidence intervals (CI). Data were pooled using the random effects model. Main results: Nineteen RCTs (820 children enrolled; 773 evaluated) were included. Most studies were small. Eleven studies were at low risk of bias for allocation concealment and only four studies were at low risk of performance bias. Fifteen, eight and 10 studies were at low risk of detection bias, attrition bias and reporting bias respectively. Cyclosporin when compared with placebo or no treatment significantly increased the number of children who achieved complete remission. However this was based on only eight children who achieved remission with cyclosporin compared with no children who achieved remission with placebo/no treatment in three small studies (49 children: RR 7.66, 95% CI 1.06 to 55.34). Calcineurin inhibitors significantly increased the number with complete or partial remission compared with IV cyclophosphamide (2 studies, 156 children: RR 1.98, 95% CI 1.25 to 3.13; I2 = 20%). There was no significant differences in the number who achieved complete remission between tacrolimus versus cyclosporin (1 study, 41 children: RR 0.86, 95% CI 0.44 to 1.66), cyclosporin versus mycophenolate mofetil plus dexamethasone (1 study, 138 children: RR 2.14, 95% CI 0.87 to 5.24), oral cyclophosphamide with prednisone versus prednisone alone (2 studies, 91 children: RR 1.06, 95% CI 0.61 to 1.87), IV versus oral cyclophosphamide (1 study, 11 children: RR 3.13, 95% CI 0.81 to 12.06), IV cyclophosphamide versus oral cyclophosphamide plus IV dexamethasone (1 study, 49 children: RR 1.13, 95% CI 0.65 to 1.96), and azathioprine with prednisone versus prednisone alone (1 study, 31 children: RR 0.94, 95% CI 0.15 to 5.84). One study found no significant differences between three agents (cyclophosphamide, mycophenolate mofetil, leflunomide) used in combination with tacrolimus and prednisone. One study found no significant difference in the percentage reduction in proteinuria (31 children: -12; 95% CI -73 to 110) between rituximab with cyclosporin/prednisolone and cyclosporin/prednisolone alone. Two studies reported ACEi significantly reduced proteinuria. Authors' conclusions: To date RCTs have demonstrated that calcineurin inhibitors increase the likelihood of complete or partial remission compared with placebo/no treatment or cyclophosphamide. For other regimens assessed, it remains uncertain whether the interventions alter outcomes because the certainty of the evidence is low. Further adequately powered, well designed RCTs are needed to evaluate other regimens for children with idiopathic SRNS. Since SRNS represents a spectrum of diseases, future studies should enrol children from better defined groups of patients with SRNS.