The effectiveness of the cognitive interview (CI) technique has been demonstrated in experimental studies of eyewitness memory conducted in the USA, Germany, and the UK. Much of the research, however, has used college students as interviewers rather than professionals who regularly interview witnesses (e.g. police officers). The aim of this research was to examine the effects of such CI training using experienced police olficers with established interviewing styles. An armed robbery was staged and information was elicited in witness interviews. The CI did not significantly increase correct recall but tended to produce more suppositions and errors. A qualitative analysis of interviewer behaviour showed that many officers had difficulty in applying the new cognitive techniques and in avoiding the use of closed and leading questions. The paper addresses two issues: first, that of training experienced police officers who have received relatively little prior training in investigative interviewing, and second, the extent to which we can generalize from the laboratory data elicited in previous studies of CI.In 1992 all police officers in England and Wales were given a 57-page booklet on investigative interviewing produced by a team of experienced detectives on behalf of the Association of Chief Police Officers and the Home Office (the relevant government ministry). The booklet recommended cognitive interview (CI) techniques and described them. The CI is a procedure for conducting interviews that has emerged from psychological knowledge and research about the organization and access of information from memory. The CI has the potential to be tested and refined for application in several fields. The most notable application of the CI is in police interviews of witnesses (Fisher, Geiselman, and Ama.dor, 1989;George, 1991). This, together with earlier research using college students as interviewers, (Geiselman, Fisher, Mackinnon, and Holland 1985) suggests that following a brief training (ranging from a few hours to two days), it is possible for interviewers to produce substantial We are grateful for the assitance of Roy Pritchard and Mark !:mith (Dorset Police Training School, Headquarters, Winfrith) in the organization and running of the study, and to Muriel Maupoint and Patrick Gwyer for their help with codinglscoring of transcripts. Thanks also to Inspector Richard George and anonymous reviewers for their comments on this paper, and to Orla Cronin for her contribution to the construction of training and evaluation materials.