Background and Aim: The role of cytokines in the immune-pathogenesis of idiopathic nephrotic Syndrome (INS) had been widely postulated. Some cytokines, most importantly IL-4, have been also involved in the pathogenesis of asthma. The majority of INS patients do exhibit a form of atopy including asthma, implying a common pathological background of both diseases. The aim of this study is to explore the role of IL-4 in the pathogenesis of a relapses in INS patients with Asthma compared to those without concomitant asthma. Patients and Methods: Demographic, biochemical data and mean urinary IL-4 levels were evaluated in 41 steroid-sensitive INS patients and 30 matched Asthmatic controls without INS or atopy. Mean urinary IL-4 levels in INS patients were compared to controls as well as in the 2 subgroups of INS patients: Group A (INS with Asthma, n=14) and Group B (INS patients without Asthma or atopy, n=27) to controls during relapse and remission. Results: Mean age of patients at study was 8.9 ± 3.5years (range: 49 months-15 years). Male: Female ratio was 28:13. Mean serum creatinine was 49 ± 10 μmol/l and mean serum albumin was 29 ± 10 g/L. Mean urinary IL-4/Cr in INS patients during relapse and remission was 12.170 ± 20.013 pg/μmol and 15.269 ± 41.275 pg/μmol, respectively (P=0.716). Both levels were not statistically different when compared to controls (24.78 ± 89.51 pg/μmol) (P=0.5431 and P=0.662, respectively). Mean urinary IL-4/Cr level was significantly higher in Group A vs. Group B during relapse (28.22 ± 26.12 pg/μmol vs. 2.73= ± 3.38 pg/μmol, P=0.003) and during remission (31.52 ± 57.13 pg/μmol vs. 1.04 ± 1.48 pg/μmol, P=0.004). Group A patients had a higher mean urinary protein excretion and a longer duration to remission than group B patients. Conclusion: INS patients with asthma have a higher IL-4 excretion which might increase the severity and duration of proteinuria. The coexistence of Asthma in INS patients requires an early and abrupt treatment of relapses.