The results of treatment with extracorporeal shock wave lithotripsy (ESWL) were recorded in 1067 patients with renal calculi during their first admission to hospital. All treatments were performed in an unmodified Dornier HM3 lithotripter according to the original recommendations whereby the generator voltage was usually set between 18 and 23 kV. The stones in kidneys treated with ESWL alone were first classified into four different types (A. B. C. D) and after which a further subgrouping was carried out according to the number and sites of stones in the renal pelvis or calyces. The number of shock-waves. the energy index. the duration of treatment, and length of hospital stay as well as the therapeutic results after four weeks and six months were recorded for the different subgroups. An approximate estimate of the stone volume was calculated from measurements on a plain abdominal radiograph. The mean stone volume, number of shock waves, energy index, duration of treatment, and length of hospital stay increased progressively and significantly from group A to group D. The stone volumes and the energy indexes in the different subgroups within each type were distributed around levels that clearly differed between the types. Although minor variations were observed similar patterns also were recorded for the retreatment rate, the total duration of treatment, and the length of hospital stay. The therapeutic result, expressed as satisfactory disintegration, showed roughly similar results within each group but, as expected, the success rate decreased when more complicated stones were treated. Although stones located in the renal pelvis were often bigger than calyceal stones, the former seemed to disintegrate more easily.(ABSTRACT TRUNCATED AT 250 WORDS)