There has been a gradually increasing need for using video in multimedia communication services. As there is a big tendency to move towards a third-generation universal telecommunication environment, the necessity to carry video information on mobile networks increases. Since mobile environments naturally impose a high level of hostility against carried intelligence, error resilience techniques must be formulated and applied on video coders to render their bit streams more immune to deteriorated channel conditions. The authors discuss bit rate variability in block based video coders, the effects of channel errors on an H.263 video bit stream, and error resilience improvement. (6 pages)