Cryptophthalmos may be partial or complete, unilateral or bilateral, apparently nonsyndromal or syndromal. A recent study of 2 stillborn infants at the University of Utah prompted an analysis of the developmental aspects of the syndromal form (Fraser syndrome). We conclude that, per se, cryptophthalmos is a developmental field defect on the basis of heterogeneity (autosomal dominant and recessive forms) and phylogeneity (occurrence also in the pheasant, rabbit, pigeon, dog, and mouse). In humans this autosomal recessive disorder maps to 4q21, is homologous to the bleb (bl/bl) mouse, and is due to mutations in the FRAS1 gene that codes for a 4007 amino acid protein 85% identical to the Fras1 gene of the bleb mouse. Commonest anomalies in humans are cryptophthalmos, cutaneous syndactyly of digits, abnormal ears and genitalia, renal agenesis, and congenital heart defects. Almost half of affected infants are stillborn or die in infancy, and mental retardation is common. The pathogenesis evidently involves abnormal epithelial integrity during prenatal life. Older (mostly German) publications, some dating to the 19th century, provide a fascinating historical insight into the process of syndrome delineation.