We treated 19 selected patients with calculi in 21 caliceal diverticula with extracorporeal shock wave lithotripsy (ESWL). By limiting this treatment to patients with relatively small (less than 1.5 cm.) calculi associated with a radiographically patent diverticular neck, a stone-free state was initially achieved in 11 patients (58%). Of 14 patients with flank pain before ESWL 12 (86%) were rendered symptom-free or markedly improved, often independent of a stone-free state. Extended followup in 13 patients for 12 to 49 months (mean 23.8 months) after ESWL revealed recurrent stones or stone growth in only 1. Although pain relief has remained constant for those initially rendered symptom-free, recurrent infection has been documented in 6 (67%) of 9 patients with infection before ESWL. We conclude that ESWL for selected patients with calculi in caliceal diverticula can achieve a relatively high initial stone-free rate and that recurrent stones may not be inevitable. Treatment in this setting also may provide long-term symptomatic relief that is often independent of a stone-free state. However, recurrent infection is not unusual, especially when associated with residual calculi. Considering the relatively noninvasive nature of this approach, ESWL should be considered an acceptable form of primary management for selected patients with calculi in caliceal diverticula.