OBJECTIVE: To describe the presentation and genetic transmission of ciliary dyskinesia syndrome associated with hydrocephalus and mental retardation in 3 generations of a family. PATIENTS AND METHODS: A large Jordanian family included 9 individuals in 3 generations with recurrent pulmonary infections; 4 male siblings have been diagnosed as having mental retardation, and a maternal uncle was believed to have been similarly affected. Chromosome analysis of the family showed a normal karyotype. RESULTS: Electron microscopy of the nasal cilia from 3 affected siblings showed features of primary ciliary dyskinesiComputed tomographic scans of the brains of all 4 affected siblings showed hydrocephalus. CONCLUSIONS: The recurrent pulmonary infections and hydrocephalus in this large Jordanian family are likely related to ciliary dyskinesia, which appears to follow an autosomal recessive mode of inheritance. The unusual presentation of ciliary dyskinesia, hydrocephalus, and mental retardation may be due to a new genetic mutation