The effects of chemotherapy on the metastasis of retroperitoneal lymph nodes from testicular cancer have been generally evaluated with bi-dimensional imaging methods. Since the structure of these lymph nodes seems to be complicated, it is expected that three dimensional imaging methods could achieve more correct evaluation of the disease extension and the treatment effects when compared with bi-dimensional ones. The present study was undertaken to reconstruct the three dimensional imaging from CT films using personal computer system. Twenty one patients with bulky retroperitoneal nodal metastases were examined before and after chemotherapy. The evaluation of treatment effects based on three dimensional imaging method reflected the clinical course more adequately than the bi-dimensional one. When shrinkage rate of the tumor volume was less than 65%, viable tumor cells remained in all cases. Only one of six cases with more than 90% shrinkage revealed viable tumor cells. All patients in whom the metastases were estimated to be more than 100 cm3 in volume before chemotherapy and less than 50 cm3 after chemotherapy were shown to have completely necrotic tissues. In conclusion, three dimensional imaging was useful to estimate the post-treatment volume and shrinkage rate which correlated to the effects of treatment and prognosis.