We used decision analysis to compare the conventional strategy of biopsy-tailored therapy with alternative strategies not using renal biopsy in treating adults with idiopathic nephrotic syndrome. We evaluated data on steroid and platelet-inhibitor therapies and a new clinical strategy, empiric sequential therapy. This sequential approach involves use of short-term alternate-day steroid agents, followed by long-term platelet inhibitors for persistent nephrotic syndrome. Our results indicate that, contrary to usual practice, use of renal biopsy is not necessary in caring for adult patients with idiopathic nephrotic syndrome; empiric short-term alternate-day steroid therapy is equally efficacious. If the benefits of platelet-inhibitor therapy for treating membranoproliferative glomerulonephritis are confirmed, empiric sequential therapy also will be equally efficacious. Our study shows how decision analysis can be used to identify superfluous diagnostic procedures.