Intracellular energy metabolism was studied by phosphorus magnetic resonance spectroscopy in the brains of 27 preterm and term infants with increased echodensities consistent with hypoxic-ischaemic injury and 18 comparable normal infants. In the normal infants the phosphocreatine (PCr)/inorganic orthophosphate (Pi) ratio increased significantly from 0.77 +/- 0.24 (95% confidence limits) at a gestational plus postnatal age of 28 weeks to 1.09 +/- 0.24 at 42 weeks. 9 of the 15 infants with increased echodensities whose PCr/Pi ratios fell below the normal range died; in all 6 survivors cerebral atrophy developed (cysts in brain tissue or microcephaly). In contrast, all 12 infants with increased echodensities whose PCr/Pi ratios remained within the normal range survived, although cerebral atrophy developed in 3 with ratios towards the lower limit of normal.