This prospective case control study was carried out in Renal and Dialysis Unit of Dhaka Shishu Hospital, Bangladesh from January 2004 to December 2004 to determine serum IgE level in frequent relapse Idiopathic nephrotic syndrome and to evaluate any role of IgE in the rate of relapse. Thirty cases of frequent relapse (FR) Idiopathic nephrotic syndrome (INS) were considered as cases and thirty cases of infrequent relapse nephrotic syndrome (IRNS) were considered as control. Serum IgE level was measured in all patients at the time of relapse and again four weeks after steroid treatment when patient was in remission. The test statistics used to analyses the data were descriptive statistics, Chi-square probability test, Student's "t"-Test, Mann Whitney test and Wilcoxon Signed Rank test. Majority of the patients' age in both the groups was between 2-6 years. The male female ratio in FR group was 2:1, while that in IR group was 3:2. Forty percent of the frequent relapsers and 30% of infrequent relapsers were found to possess the history of atopy. However, the difference between the two groups was not statistically significant (p>0.05). The mean serum albumin in FR was observed to be significantly lower (13.73±0.59 gm/L) than that in IR (15.73±0.67 gm/L) (p<0.05). Mean serum IgE at the time of relapse in FR (1791±95 IU/mL) was found to be more than 3 times higher than that in IR (560±50 IU/mL) (p<0.001). Serum IgE level at the time of remission has decreased to almost normal in IR group (204±21 IU/mL) but it was still found 5 times higher in FR group (1086±79 IU/mL) (p<0.001). Serum IgE level is high in both FR and IR groups of nephrotic syndrome at the time of relapse. It reverts back to normal in IRNS but persistently and significantly high in FR group in both relapse and remission. Level of the serum IgE can be used as a predictor of FRNS.