We administered a dose-down chemotherapy, which was a combination of carboplatin 100 mg/body (AUC 3.0, day 1) and CPT-11 30 mg/m2 (day 1, day 15) to the patient with a poor performance status of extensive small-cell lung cancer with renal failure. Hemodialysis was performed two hours after the chemotherapy. We measured plasma levels of total-platinum and CPT-11 and metabolic products (SN-38) after the hemodialysis. The results of pharmacokinetic study showed a high level collection of total-platinum caused by carboplatin and SN-38, and that was caused by CPT-11 in the blood. Although the grade 3 of granulocytopenia was found, the decrease in tumor marker and an improvement of the ADL were confirmed. It thought that this chemotherapeutic regimen was effective for small-cell lung cancer with renal failure undergoing hemodialysis. Further study is needed for a selection of suitable chemotherapeutic regimens, an optimal dosage of each drug and timing of hemodialysis.