We developed a new telemedicine system to monitor the condition of continuous ambulatory peritoneal dialysis (CAPD) patients by using a cellular telephone and an Internet Web site. All data for the CAPD patients--blood pressure, heart rate, body weight, ultrafiltration volume, and urine volume--are collected and sent directly by cellular telephone to a data server that was constructed at the NTT DoCoMo Company data center. The system is directly connected to Internet by application service provider (ASP) technology. Anywhere, at any time, each patient can confirm changes in their data in graph form by using a cellular telephone or a computer connection to an Internet Web site. The average of each type of data is calculated and shown at the Web site. All data collected by cellular telephone are calculated and, in real time, sent directly to the treating physician's office over the Internet. Abnormal data are sent directly to the treating physician's office and shown in the host computer with an emergency signal (emergency alarm system). In addition, CAPD patients can easily contact the medical staff in the Kidney and Dialysis Center of Saitama Medical School (main hospital) using the same telemedicine system. We are using this telemedicine system for 46 CAPD patients being treated by Saitama Medical School. The cost of using the system is just US$3.00 or less per month for each patient. This newly developed system has great advantages for CAPD patients, especially elderly and handicapped patients. The system can be expanded into a network that serves all CAPD patients and all hospitals in Japan.