Data on the occurrence of endemic nephropathy (EN) and urinary tract and other cancers in an endemic region of Vratza district, Bulgaria, for the years 1965-1974, are presented. In endemic villages a high incidence of urinary tract tumours, affecting in particular the renal pelvis and ureter, closely correlated with the EN incidence and mortality rates. In the villages with high and moderate EN incidences urinary tract tumours are the most common neoplasms. They account for 25% of all tumour sites in males and 30% in females. In hyperendemic villages age-adjusted incidences in EN and urinary tract tumours were 506/10(5) and 104/10(5) in females, and 315/10(5) and 89/10(5) in males respectively. EN mortality in these villages accounted for over 40% of all deaths in females and about 30% in males. Both diseases displayed peculiar geographic clustering. Females and middle-aged persons were most often affected. Urinary tract neoplasms were often multiple and nearly 90% of them originated in the uro-epithelium. In endemic and non-endemic villages of the region studied, the frequency and pattern of non-urinary tract cancers were rather similar, with statistical values close to those of the rural population of Vratza District and Bulgaria as a whole.