The effects of extracorporeal shock-wave (SW) exposure on the kidney were investigated in dogs using a Dornier kidney lithotriptor HM3. The SW was generated by spark dischrge at 20KV and was focussed on the lower part of either kidney. Before and after the exposure of 500 and 1000 shots of SW, the renal blood flow of the affected and contralateral kidney was measured by the microsphere method. The blood flow of the affected kidney decreased, but was comparable to that of the contralateral kidney immediately after the 1000 shots of SW. Renal scintigraphy using ^99mTc-DTPA was performed before the exposure of SW, and 30 minutes, 1 week, 2 weeks and 4 weeks after the exposure. The renograms were evaluated by the following parameters: T_max (time required to reach maximum radioactivity), RA_max ratio (maximum radioactivity of the affected kidney/that of the contralateral kidney) and T_1/2 (the half-life of elimination). T_max was significantly prolonged for the affected kidney 30 minutes after the exposure, while that for the contralateral kidney was shortened. The RA_max ratio was decreased 1 week after the exposure. T_1/2 was significantly prolonged 30 minutes after the exposure, which was observed till 2 weeks later. The scintigraphy also showed a slight enlargement of affected site. The histological study showed a hemorrhage in the peritubular space, indicating rupture of the peritubular capillaries. In conclusion, the main effect of SW exposure on the kidney was the rupture of the peritubular capillaries, resulting in temporary and reversible deterioration of renal function.