Recently, the improtance of the ISDN has been emphasized for the new services in the future information society. In this paper, new application of statistical multiplexer which can be used for CCITT D-channel multiplexing is suggested. The basic architecture of statistical multiplexer which can interleave eleven 16Kbps D-channels into one 64Kbps B-channel is also proposed. The necessary buffer size was estimated by computer simulation considering data traffic intensity, signal arrival length distribution and buffer overflow probability. Based on this buffer size, the basic architecture of the statistical multiplexer has been survetyed and hardware design principles are also studied.