Peters Plus syndrome is an autosomal recessive disorder characterized by anterior eye-chamber abnormalities, disproportionate short stature, and developmental delay. After detection of a microdeletion by array-based comparative genomic hybridization, we identified biallelic truncating mutations in the beta 1,3-galactosyltransferase-like gene (B3GALTL) in all 20 tested patients, showing that Peters Plus is a monogenic, primarily single-mutation syndrome. This finding is expected to put Peters Plus syndrome on the growing list of congenital malformation syndromes caused by glycosylation defects.