Polypeptide elongation factor Tu has been purified from E. coli as Tu.GDP and Tu.Ts complexes, and both of them were crystallized (K. Arai, M. Kawakita, and Y. Kaziro, J. Biol. Chem., 247, 7029 (1972)). In this communication we describe a procedure for the preparation of crystalline Tu-GTP, Tu.Gpp(CH2)p, and (phenylalanyl-tRNA).Tu.GTP complexes. The preparation of (phenylalanyl-tRNA).Tu.Gpp(CH2)p is also described.