Crystals have been obtained of protein L1 from the large ribosomal subunit of an extreme thermophile. Thermus thermophilus, using a mixed solution of ammonium sulphate/methane pentanediol. The crystals belong to the space group P2(1)2(1)2, with cell parameters a = 82.7 A, b = 63.4 A, c = 44.7 A. They diffract X-rays to 2.3 A resolution.