This paper describes a comprehensive TV audience reaction service which has recently been initiated on a pilot basis for Independent Television in the U.K. The service as a whole has been designed as a flexible research instrument, capable of providing a variety of measurements and indications of all the ways in which the TV audience is reacting towards, and thinking about, the programme transmitted on the three different channels - BBC 1, BBC 2 and ITV - at present available. The primary emphasis of this paper is, however, on those parts of the service which provide measures of audience evaluation of programmes: that is to say, diagnostic measures indicating the ways in which programmes are judged, thought about and compared, in addition to simple measures of appreciation (i.e. enjoyment or involvement) . The paper is presented from the point of view of the user, rather than the practitioner of research, and is therefore more concerned with the applications of the service than with the technical details of its structure and operation. The techniques used, however, are particularly suited to the problems of TV audience research and a general description of them is necessary in order fully to understand their practical applications.