Balkan endemic nephropathy (BEN) is a human chronic tubulointerstitial renal disease that occurs in rural areas of some Balkan countries. The disease is insidious and fatal, and mostly affects persons in their sixties or seventies. BEN areas have unusually high rates of otherwise rare upper urinary tract tumors (UTT). Since extensive production of reactive oxygen species leading to oxidative stress has been implicated in tumor development, the aim of this study was to see whether oxidative stress is involved in the development of BEN and UTT. Urine samples were collected from a BEN village (N = 22) and a control village (N = 16) residents and analyzed for malondialdehyde (MDA) and 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG). The levels of both oxidative stress parameters were significantly higher in the BEN village residents than controls. However, there was no correlation between MDA and 8-oxodG results. Our results confirm that oxidative stress could be implicated in development of both, BEN and UTT.