We have studied a sibship with one confirmed and three probable cases of the Marden-Walker syndrome (MWS). Our patient had the major manifestations of blepharophimosis and squint; narrowly arched palate with micrognathia; small mouth and mouth-breathing; facial deformities and distortions; congenital muscle weakness with resulting scoliosis; mild pectus excavatum; camptodactylies and hip and finger joints subluxation. In addition, he had small, apparently low-set and slightly malformed auricles with a unilateral preauricular tag. However, he had no apparent renal or cardiovascular involvement. Results of CPK, EMG, and of histochemical, light microscopic, and ultrastructural studies of muscle biopsy do not suggest a primary myopathy but rather CNS related weakness/hypotonia with small muscle mass and hypoactive DTRs. This pathogenetic hypothesis is confirmed by the presence of severe mental retardation and minor brain changes suggesting cortical atrophy. In five previously reported cases there has been microcephaly. Phenotype analysis does not convince that the MWS is a true malformation syndrome, but rather hints at the possibility of a congenital metabolic dysplasia. Genetic analysis demonstrated autosomal-recessive inheritance in this and two other instances; primarily sporadic occurrence leaves open the possibility of genetic heterogeneity.