This article argues that HRM is by nature a multidisciplinary subject area, and that it has traditionally been closely associated with the field of industrial relations (IR). However, it appears to have increasingly been taken over by industrial and organisational (I-O) psychology, and in the process increasingly associated with organisational behaviour, which has also been taken over by I-O psychology. Coupled with the narrowing and marginalisation of IR, this has meant an increasing ‘psychologisation’ not only of the study of HRM, but of the study of employment relations in general. This article discusses why this appears to have been happening, what its implications might be and what (if anything) might be done about it. Focus is on developments within North America, although the issues raised apply, perhaps, to different degrees, across liberal market countries and possibly beyond.