The aim of this prospective study was to evaluate the diagnostic role of somatosensory evoked potentials (SEP) during the neonatal period with regard to maturational changes and prognostic value in perinatal hypoxic-ischemic encephalopathy. Median nerve SEP analysis was performed in 31 healthy infants (group A1, 33-35 weeks, n = 10; group A2, 36-37 weeks, n = 11; group A3, 38-41 weeks, n = 10) and in 10 term infants with hypoxic-ischemic encephalopathy (group B). Cortical latency N1 and central conduction time values were analyzed for group A in relation to postconceptional age and postnatal age and for group B in relation to degree of hypoxic-ischemic encephalopathy and neurodevelopmental outcome (at the mean age of 6.6 + or - 1.6 years). Central latencies were correlated with postconceptional age but not postnatal age. Mean N1 latency and central conduction time values did not differ significantly between groups A1 and A2; the most pronounced decrease was between groups A2 and A3 (postconceptional ages 36-37 vs 38-41 weeks). In group B, central latencies were prolonged, compared with controls (P < 0.001), but were not significantly correlated with long-term outcome in patients with moderate hypoxic-ischemic encephalopathy (n = 6). Neonatal SEP analysis thus is an objective and noninvasive method for assessing functional integrity of the somatosensory pathway. In term infants, SEPs are a valuable additional tool for early diagnosis of hypoxic-ischemic encephalopathy, but are not prognostic of neurodevelopmental long-term outcome in moderate hypoxic-ischemic encephalopathy.