Increasing evidence suggests that nuclear factor κB (NF-κB) plays a pivotal role in many glomerulopathies. Therefore, the aim of the present study was to determine the tubular immunoexpression of NF-κB in non-proteinuric (n = 22) and proteinuric patients (n = 16) with IgA nephropathy (IgAN). Another purpose of this study was to examine the possible relationship between NF-κB immunoexpression and proteinuria, interstitial fibrosis as well as interstitial infiltrates. Tubular immunoexpression of NF-κB, interstitial monocytes/macrophages, T lymphocytes, B lymphocytes and interstitial area were determined using a computer image analysis system. The mean values of the tubular immunoexpression of NF-κB, interstitial area and interstitial monocytes/macrophages were in proteinuric IgAN patients significantly increased compared to non-proteinuric IgAN cases, whereas interstitial T and B lymphocytes did not differ between these groups. In proteinuric patients, tubular immunoexpression of NF-κB was highly significantly positively correlated with the degree of proteinuria. Moreover, in both the non-proteinuric and the proteinuric groups with IgAN, tubular immunoexpression of NF-κB was positively correlated with the interstitial area and interstitial monocytes/macrophages. Our findings raise the possibility that proteinuria causes tubular overexpression of NF-κB and, in the process, recruitment of monocytes/macrophages and tubulointerstitial injury in IgAN patients.