One hundred eighty-three flash frozen, liquid-liquid diffusion and batch method protein and virus crystallization samples were launched aboard the Space Shuttle Discovery on June 27 (STS-71) and transferred to the Russian Space Station Mir on July 1, 1995. They were returned to earth November 20, 1995 (STS-74). Subsequent examination showed that of the 19 types of proteins and viruses investigated, 17 were crystallized during the period on Mir. The experiment demonstrates the utility of this very simple and inexpensive approach for the crystallization of biological macromolecules in space over extended time periods. The distribution of crystals among the three types of containers used indicated small samples yielded results equal or better than larger samples and that long diffusion path lengths were clearly better. Distribution of crystals within the container tubes showed a striking gradient of quality and size that indicated long, narrow tubes yield superior crystals, as predicted from other work based on crystallization in capillaries.