The vast literature on performance appraisal produced over the last twenty years has perhaps been rather stronger on opinion than on fact. Many books and articles have concentrated on what, in the light of their authors' experience, the aims and objectives of appraisal should be and on how managers can best be trained to achieve them. The overall aim of the studies was to assess the way in which the interviews were being carried out and the results they achieved. Turning to the way in which evaluation studies were typically mounted, one of the first steps was to consult the trade unions representatives of the department concerned. Consultation with the unions at national level had already taken place and agreement reached on carrying out studies of this kind, but it was essential to obtain the active co-operation of the union officials within each department.