[en] The effect was studied of selective x-irradiation of the cerebellum (100 R daily in the first 10 days after birth) on the maturation of glucose metabolism and the development of metabolic compartmentation, in 10-, 16-, and 23-day-old rats by using, respectively, [2-¹⁴C]glucose and [1-¹⁴C] acetate (40 μ Ci/100 g body weight each) as precursors. At day 10 significant changes, in comparison with the unirradiated controls, were observed: aspartate and γ-aminobutyrate, respectively, contained 36 percent and 64 percent more and glutamine 42 percent less glucose-carbon combined in amino acids; the glutamine/glutamate specific radioactivity ratio (RSA) was 25 percent less, and the conversion of both glucose and acetate carbons into acid-insoluble constituents was markedly reduced. However, in the postirradiation period both the conversion of glucose carbon into amino acids, and the RSA of glutamine after the administration of [¹⁴C]acetate increased in a more or less normal fashion, although certain quantitative differences were noted. It seems, therefore, that the normal progress of biochemical differentiation was only affected to a small degree by the irradiation of the cerebellum, although the treatment interfered severely with cell proliferation. (U.S.)