The use of recall aids as a stimulus to the memory of informants has been most highly developed in media research, and it is from this field that I draw the two examples which I wish to. discuss today. The I.P.A. National Readership Survey is a continuing survey, that is to say, fieldwork goes on continuously with each quarter's sample being a self-contained sample in itself. The survey has been carried out for more than three years now and well over 50,000 interviews have been taken, so that there is a considerable body of data to study.