We previously reported the detection of an increased subpopulation of cytotoxic T lymphocytes in patients with Balkan (endemic) nephropathy (BEN) and in area controls (individuals free of clinical syndrome but born in a BEN endemic area and having a family history of BEN). Extending the flow-cytometric analyses to other populations of peripheral blood leucocytes, we found a decrease in the proportion of B lymphocyte subset and an increased proportion of eosinophils in BEN patients and in area controls. Although these numerical alterations cannot be categorically linked to the aetiopathogeny of the disease, it is presumed that they can be induced by the same factor(s) causing the kidney damage, through a direct haemato- and lymphotoxic effect.