Seven individual members with incontinentia pigmenti are described from a family spanning four generations. The natural history of the cutaneous, ocular, hair, and dental anomalies is described for each involved member. In addition, a previously undescribed ectodermal defect, woolly-hair nevus, appeared in several affected members of this family. Evidence is offered to support the theory that the pattern of inheritance of incontinentia pigmenti is by linkage of the gene on the X chromosome acting as a dominant gene in females and lethal in males.