A simple system is described for classification of patients with urolithiasis treated with extracorporeal shock wave lithotripsy (ESWL). According to the size and number of concrements in each kidney the patients were subgrouped in six different ESWL-types (A-F). The main purpose was thereby to be able to discriminate between different stone situations regarding the need for resources and to evaluate the therapeutic results in an appropriate way. Of 709 patients treated with ESWL during the first year, 2% were of ESWL-type A, 46% of type B, 24% of type C, 16% of type D, 5% of type E, and 7% of type F. There was a good relationship between ESWL-type, number of shock waves and duration of the treatment session, number of ESWL-sessions, and duration of hospital stay. With knowledge of the ESWL-type distribution in a group of patients with urolithiasis this classification provides a basis for estimates of treatment capacity and required number of beds. With a weekly capacity of 24 treatments the required number of beds usually varied between 20 and 25. The hospital stay varied between 2 and 35 days, with the longest hospital stay recorded for patients belonging to ESWL-type E undergoing a combined procedure with percutaneous surgery, ESWL, and often irrigation with hemiacidrin. The presented system for classification might be a useful tool for planning, organization and assessment of renal stone treatment based on ESWL.