Crystals have been obtained of protein L30 from the large ribosomal subunit of an extreme thermophile, Thermus thermophilus, using ammonium sulphate as a precipitant. The crystals belong to space group P3(1)12 with cell parameters a = b = 64.2 A, c = 78.3 A. They diffract X-rays to at least 2.3 A resolution.