A National Survey of the abilities of profoundly deaf children was commissioned by the Donaldson Trust, Edinburgh in 1963 and still continues. This survey has registered the performance of selected samples of profoundly deaf children on a wide range of sensory, personality and cognitive tests and ratings together with some sociological background data and details derived from medical records. The following study is mainly based on the results of the cognitive aspects of the survey data and is further limited to the 219 profoundly deaf children from ten Scottish schools who have been subjected to tests and follow-up enquiries to date.