Balkan endemic nephropathy (BEN) is an acquired, environmental, polytopical disease of the entire urinary tract, with long latency. Tubulointerstitial chronic nephritis, urotheliomas of all localities, and renal cell carcinoma occur with a significantly higher frequency in the affected population. These represent only clinical manifestations of one unique nosological entity. BEN occurs in focuses. Within them, it agglomerates in households, without any evidence of hereditary background. Patients with various clinical manifestations of the disease can be simultaneously found within one single household. BEN appears equally among members of different ethnic groups. Its aetiology is not clear enough. There is no evidence of a causal relationship with silicon compounds, heavy metals and viruses. Much attention has been recently focused on research of the aetiological role of mycotoxins, mainly ochratoxin A. Toxic and carcinogenic agents of natural origin are commonly accepted as the major cause of BEN.