As a lot of programs and contents such as movie files are being delivered via the Internet, and copies are often stored in distributed servers in order to reduce the load on the original servers, to ease network congestion, and to decrease response time. To retrieve an object file, existing methods simply select one or more servers. Such methods divide a file into equal pieces whose size is determined a priori. This approach is not practical for networks that offer variable bandwidth. In order to more utilize variable bandwidth, we propose an adaptive downloading method. We evaluate it by experiments conducted on the Internet. The results show that the new method is effective and that it will become an important network control technology for assurance.