Network bandwidth has always been a key issue for multime- dia protocols. Many potential users of networked multime- dia protocols will continue to have low bandwidth network connections for some time: copper wire ISDN, infra-red, cel- lular modems, etc.. Compression provides potential relief for users of slow networks by increasing effective bandwidth. Higher Bandwidth X (HBX) introduces a new technique, based on arithmetic coding and statistical modeling, for compressing structured data. Applied to the X networked graphics protocol, this technique yields 6.3:1 compression across a representative set of traces, performing twice as well as the popular LZW-based Xremote compression proto- col. HBX's coding techniques are generally applicable to the graphics and imaging subset of multimedia protocols. Future work will determine whether HBX's coding techniques can be applied to audio and video streams as well.