Since 1996, a European network has been organized from Rennes, France and holoprosencephalic files were collected for clinical and molecular study. Familial instances of typical and atypical holoprosencephaly (HPE) were found in 30% of cases. All affected children had psychomotor delay with microcephaly, often associated with endocrine, digestive, and respiratory abnormalities, and thermal dysregulation. Among 173 subjects in the molecular study, 28 heterozygous mutations were identified (16%): 15 SHH mutations, 6 ZIC2 mutations, 5 SIX3 mutations, and 2 TGIF mutations. © 2004 Wiley-Liss, Inc.