Objective: To get information on the distribution of stone burdens in an average and representative group of Swedish stone forming patients requiring active removal of stones from the kidneys or ureters and to compare different methods for assessing the stone burden. Methods: A computerised device was used to measure the total stone surface area (Ameasured) of 599 stone situations in kidneys and ureters in a consecutive group of patients referred to active stone removal. These measurements were compared with the large and short transverse diameters of the greatest stone, the sum of the largest diameters of the stones, the arithmetically calculated surface area (Acalculated) as well as with the stone-types (A-F) previously described. Result: There were 483 stone situations with one and 116 with more than one stone. The stones were found in 407 men and 192 women. In 343 cases were the stones on the left side and in 256 on the right side. There were 34 staghorn stones. Of the examined stone situations 250 were in the kidney and 349 in the ureter. An Ameasured above 300 mm2 was recorded in 7% of all stone situations. The corresponding numbers for Ameasured above 200 mm2, 500 mm2 and 700 mm2 were 13%, 4% and 3%, respectively. When staghorn stones were excluded, good correlations were recorded for all variables but the best correlation was found between Ameasured and Acalculated. A revision of the previously published stone-type subgroups is suggested based on the following limits for the stone surface area: A = 30 mm2, B = 31-300 mm2, C = 301-700 mm2 and D > 700 mm2. Conclusion: The distribution of stone situtations with different stone burden in an average Swedish population is described. With the exception of staghorn stones and stones with extremely irregular form an acceptable estimate of the stone surface are can be arithmetically derived from the length and the width of the stone. © 2003 Elsevier Science B.V. All rights reserved.