Iridogoniodysgenesis is an autosomal dominant disorder in which there are abnormalities in the development of the iris stroma and trabecular meshwork tissues commonly resulting in glaucoma. The unoperated eye from an affected member of a family with iridogoniodysgenesis syndrome (IGDS) was removed shortly after death. Histopathological studies showed an incomplete, normally positioned line of Schwalbe and iris stromal hypoplasia. The molecular basis underlying the disorder is a missense mutation in the RIEG gene at 4q25, mutations of which have been previously shown to cause Axenfeld-Rieger syndrome (ARS). Coupled with another report of a missense mutation of the RIEG gene in a family with IGDS, we suggest that these mutations may interfere less with gene function and thereby may be responsible for a milder phenotype than occurs in the more characteristic ARS.