The determination of RNA structures by X-ray crystallography is an exciting and developing field. At present, the crystallographic characterization of RNA is limited by the difficulty in obtaining large, high quality crystals. This paper outlines several techniques for improving the likelihood of obtaining RNA crystals, for improving the size of those crystals, and for extending the limit of the diffraction maxima. Sequence variations have proven to be more effective in changing the quality of the crystals than variations in crystallization conditions, often making the difference between obtaining true single crystals and multiply twinned crystalline material.