Holoprosencephaly (HPE) is a rare birth defect that occurs during the first few weeks of pregnancy. It results from a disturbance in the usual signaling pathways required for separation of the embryonic prosencephalon into 2 separate cerebral hemispheres. Classically four subtypes have been recognized: alobar, semilobar, lobar, and middle interhemispheric holoprosencephaly. The cause of HPE is unknown but may include genetic disorders. In most cases of holoprosencephaly, the malformations are so severe that babies die before birth. In less severe cases, babies are born with normal or near-normal brain development and facial deformities that may affect the eyes, nose, and upper lip. We report 2 cases of semilobar holoprosencephaly, diagnosed in Children's Hospital of Rabat: the first one was a fetus diagnosed by ultrasonogram at 25 weeks of gestation. The second one was a newborn at 15 days of life diagnosed by brain scan.