RESUMEN
The authors have studied the RCD spread in Vratza district according to the material of the therapeutic departments in the district for the period 1969--1973 and according to the material of the out-patient department -- polyclinical--1971--1973. During that period 16,294 patients with diseases of the urinary system were registered, 6311 out of them with RCD, i. e. 38.7 per cent. The region of Mezdra was established to be the highest affected by RCD in the district (60,8%), followed by Belaslatina region (43.4%), Vratza (40%), Kneza (37.9%) and Orejahovo the last--(22.4%). Females were established to suffer more frequently (56.7%) as compared with males (43.3%) and the peasants 51.8%) insignificantly more often in comparison with the the townsmen (48.7%). All ages are affected by the disease but most frequently the individuals aged 31--50 (49.5%). Workers (36.4%) are those that most frquently suffer of RCD in the district of Vratza, followed by employees (23.4%), cooperative farmers (21.6%), etc. The authors have established that renal calculosis affects most frequently the right kidney (56.6%) as compared with the left (40.4%) and very rarely both kidneys (2.94).