In this telephone interview, Dr Matthew Nock discusses the clinical assessment of suicide ideation and behaviour, and raises some of the problems faced by clinicians in this challenging field. He discusses in detail the development of a test known as the implicit association test which may be used in the future to help measure suicide risk without the need to rely on a patient’s self report. Talking about the common mistakes made by clinicians during clinical interview he also flags the importance of understanding a patient’s motivation and the need for clinicians to continue to develop predictive skills in assessing what is otherwise considered relatively unpredictable behaviour.