The authors describe a series of measurements of the statistics of viewphone-type video signals, with particular regard to the possible transmission of such signals over an asynchronous transfer mode (ATM) network. Measurements include the frame-to-frame differences and the cluster length distribution. It is known that with efficient picture coding, the information rate required for a constant picture quality varies significantly and creates problems in a constant-bit-rate system. The multiplexing of a number of sources in a variable-bit-rate (VBR) system is considered. It is shown that considerable reduction in the variability of the data rate is obtained. While the results are derived from one particular type of picture coder, it is expected that the conclusion will apply to other coding schemes.>