Résumé : Background: Recently, it has been reported that neuronal plasticity in the brainstem arousal pathway is related to the sudden infant death syndrome (SIDS). Tau protein may contribute to axonal development and neural plasticity; therefore, the correlation between τ protein in the brainstem and sleep apnea in SIDS was investigated here. Materials and methods: Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, including 26 cases of SIDS. The frequency and duration of sleep apnea were analyzed on all the infants, having been recorded during one night in a pediatric sleep laboratory some 3-12 weeks before death. The brainstem material was collected and immunohistochemistry of τ was carried out. The density of τ-positive elements was measured semiquantitatively. Correlation analyses were carried out between the density of τ-positive elements and the data of sleep apnea. Results: In the 26 SIDS cases, τ-positive findings were observed in the sub-pia mater in two cases, in the colloid plexus in one case, in the ependyma and subependyma in five cases, in neurons in two cases and as a general diffusion in one case. In 12 control cases, τ-positive findings were observed in the sub-pia mater in one case and in neuronal elements in three cases. No correlation was found on analysis. Conclusions: There was no correlation between the finding of τ in the brainstem of SIDS victims and the incidence of sleep apnea. © 2003 Elsevier Ireland Ltd. All rights reserved.