Cerebrospinal fluid (CSF) levels of 3-methoxy-4-hydroxyphenylglycol, 5-hydroxyindoleacetic acid, homovanillic acid, tryptophan, and gamma-aminobutyric acid were measured using high-performance liquid chromatography in 102 infants during the 1st year of life (preterm and term neonates included). CSF levels are expressed versus corrected age (postnatal days - preterm days) which reflects the stage of maturity of the central nervous system. These results are compared to those obtained in CSF of 53 victims of sudden infant death syndrome (SIDS). All components were significantly higher in SIDS than in the age-matched control group. This increase does not seem to be an artefact related to death. Indeed, under the same conditions concerning postmortem time interval before CSF sampling and analysis, the levels are not significantly higher in infants who died from a known pathology than in living infants. Moreover, in living infants as regards a pathology such as asphyxia or hypoventilation in comparison with SIDS, similar profiles are observed in some neurotransmitters or metabolites. Other studies are necessary to explore further neurotransmission systems in SIDS.