<h2>Summary</h2> Three cases of incontinentia pigmentiare reported, one of them in a boy 4 years of age. (In males the disease is extremely rare. Not more than four of the 80 cases published since 1925 have been males.) The other two cases were in girls of 1 and 4 years, respectively. Two of the cases were observed in all three stages: the vesicular, the verrucous, and the pigmented. The older child's condition was also observed in the fourth stage: the fading pigment stage. The histopathologic findings were typical for the disease, and there was blood eosinophilia in the acute early stage. The boy had various neurologic manifestations, such as convulsions in the neonatal period; strabismus and anisometropia with myopia and unilateral impaired vision; bradylalia; alopecia areata with hyperpigmentation; late eruption of defective teeth, and partial anodontia in the permanent dentition. No relationship to toxoplasmosis was found. The second case, a girl of 1 year, had typical skin changes at various ages, but no real neurologic or ophthalmologic changes. The third case, a girl of 4 years, was studied at another hospital in the early stages and transferred here in the pigmented stage. She showed, in addition to the extensive pigmentation, partial hypodontia of the permanent teeth, strabismus with amblyopia ex anopsia, anisometropia, and alopecia areata with hyperpigmentation. The etiology is discussed, and the probability stressed that incontinentia pigmenti is referable to the ecto- mesodermal polydysplastic diseases, mostly affecting the female sex.