Nine achondroplastic dwarfs were studied with computerized tomography, skull and cervical spine films, and psychometric testing. All had large ventricles that ranged from the top limits of normal to severe hydrocephalus. Three had enlarged cortical sulci. Skull and cervical spine films were typical forachondroplasia, but in addition significant asymmetry of the petrous ridge was noted. Psychometric testing disclosed generally average intelligence quotients which fell below the expected performance level in each case. These findings may be explained on the basis of the abnormal endochondral bone formation found in achondroplasia.