As described in Chapter 2 (p. 28 ff), the definition a of National Health Service hospital for the subnormal was taken to be a group of subnormal patients and their staff, whether housed together in a single complex or not, under the charge of a single Medical Superintendent or his representative. The first stage of the sample design was to prepare a list of such hospitals in Great Britain (see pp. 28-29). Eighty-two hospitals were identified for this list, but four of these had been contacted for the pilot study and, since it was felt that they should not also be included in the main study, they were removed from the list before the sample was selected. There remained 78 hospitals on the list, from which it was decided to select 35 for the study.