Background: The incidence of idiopathic nephrotic syndrome (INS) varies among countries, with Asia reporting a higher incidence in comparison with Western countries. We investigated the epidemiologic features of INS and attempted to identify factors that predispose individuals to develop end-stage renal disease (ESRD). Methods: Claims data from the Taiwanese National Health Insurance program from 1996 to 2008 were used to investigate the epidemiologic features and clinical variables of INS (International Classification of Diseases, Ninth Revision, Clinical Modification code, 581) in children younger than 18 years. Results: We enrolled 4083 children (male-female ratio, 1.91:1). During the 13 years of observation, annual incidence decreased from 9.91 to 3.36 per 100 000 children. Annual number of hospital admissions progressively decreased during the first 3 years after diagnosis. At 3.14 ± 2.77 years after INS onset, ESRD had developed in 145 (3.6%) children. Independent predictors of ESRD included older age at onset, acute renal failure (ARF), hypertensive encephalopathy, and a histologic subtype with focal segmental glomerulosclerosis (FSGS). Conclusions: Pediatric INS in Taiwan was more frequent in boys. Unlike India, the current incidence of pediatric INS in Taiwan is very similar to that reported in Western studies. Older age at disease onset, ARF, hypertensive encephalopathy, and FSGS on biopsy are important predictors of poor renal outcome.