A standard treatment has not yet been established for elderly small-cell lung cancer patients, especially when they have end-stage renal disease. We report the first case of successful chemoradiotherapy in an elderly small-cell lung cancer patient undergoing continuous ambulatory peritoneal dialysis. A 77-year-old Japanese man on continuous ambulatory peritoneal dialysis was diagnosed as having limited disease small-cell lung cancer. He received four monthly cycles of chemotherapy consisting of carboplatin at 240 mg/m(2) on day 1 and etoposide at 40 mg/m(2) on days 1 and 3. He underwent additional hemodialysis on days 1 and 3, while continuous ambulatory peritoneal dialysis continued as usual on the other days. Following chemotherapy, he underwent hyperfractionated radiotherapy to a total dose of 45 Grey, resulting in complete remission of the disease. A pharmacokinetic study showed an area under the concentration-time curve of carboplatin of 3.41 to 4.88 mg.min/mL, increasing gradually over the first three cycles, while etoposide did not show this gradual increase. The increased area under the concentration-time curve of carboplatin may have reflected a worsened renal function during chemotherapy. Despite dose reductions and favorable areas under the concentration-ime curve of carboplatin, the patient suffered grade 3-4 hematological toxicities, necessitating transfusions and a further dose reduction. The patient died of recurrent small-cell lung cancer 19 months after diagnosis.