In this study we describe two patients with congenital absence of alpha-fetoprotein (AFP). The pathological examination results, including an immunohistochemical stain, which define qualitatively the levels of AFP detected by the biochemical studies and the comparative genomic hybridization (CGH) are enclosed. A description of the suggested functions of AFP and the means of its production are set forth. An explanation is suggested for the lack of symptoms in a newborn with undetectable levels of AFP and the mechanism by which this condition might occur. © 2003 Wiley-Liss, Inc.