Aims. To find hepatic markers of perinatal asphyxia. Patients and methods. Variations in blood ammonia during the first week of life and in transaminase in serum during the first 48 hours were analysed in four groups of newly born infants (NBI): Group I or control, in which 65 NBI were included, with suspected unconfirmed infection and no other pathologies; Group A made up of 15 NBI with loss of foetal well-being (LFW) with no posterior neurological clinical features; Group III, consisting of 2 7 NBI with LFW criteria and mild hypoxic-ischemic encephalopathy (HIE); and Group IV, with 25 NBI with LFW criteria and mild HIE according to Amiel's criteria. Results. The average blood ammonia values in full-term infants remain steady during the first week of life (87 66 +/- 21.69,mug/dL), as occurs in infants with LFW but without HIE(89.08 +/- 24.69 mug/dL) and in those with mild HIE (89.08 +/- 20.75,mug/dL). In moderate HIE, the blood ammonia level rises until the third day (108.55 +/- 7.04,mug/dL) and then drops back to the initial values (p = 0.0045). When grouped by days, these values show significant differences (p = 0.04), with higher values in Group IV. The NBI with HIE presented higher levels of transaminases, especially of AST (GOT) (p = 0.000001), and this increase is proportional to its gravity. No relation was found between values of blood ammonia and transaminases. Conclusions. Both. blood ammonia and transaminases can be considered to be perinatal asphyxia markers.