This paper describes the clinical symptoms and signs of Balkan endemic nephropathy (BEN). The initial asymptomatic period followed by weakness and lassitude during renal insufficiency is emphasized. Non-characteristic lumbar pain may be present and episodes of macrohaematuria may occur. There is no fever, no severe dysuria, and no general disease preceding the symptoms. No oedema of the nephrotic type is recognized. Working capacity is unaffected until the late stage of the disease. In the advanced stages pallor of the skin and xantochromia of palms and soles are noticeable. Blood pressure is normal, but in the advanced phase may be elevated. In the uraemic phase a full uraemic syndrome is found. Urothelial tumours are frequent, occurring in 2-47% of cases; tumour cells may be found in the urine. Proteinuria of tubular type may be found early; in the uraemic phase it is constant. In the urinary sediment there are scarce white and red blood cells (the latter episodically abundant). Bacteriuria is present in about 20% of women patients. Glucosuria (less than 10%) and aminoaciduria (less than 10%) have been reported. In the early stages of BEN the urine concentration capacity is impaired earlier than renal blood flow and glomerular filtration rate. Enzymuria is present in the early phases. Tamm-Horsfall protein may be increased in the urine. Normo- or hypochromic normocytic hyporegenerative anaemia is a frequent finding. Bone marrow and leucocytes are normal. Serum proteins and immunoglobulins are not altered. Complement is normal; anti-glomerular basal membrane and anti-tubular basal membrane are negative. On radiography, kidney size varies from normal to the size of a small contracted kidney. The clinical picture of the disease is that of a slowly progressing tubulo-interstitial chronic nephritis.