The purpose of this paper is to set out informal, provisional and comprehensive but concise guidelines for mother-infant (perinatal) mental health (psychiatry), as an area of specialisation. It is informal in the sense that the authors are clinicians and researchers from many different nations, who share a common goal and vision, speaking on their own behalf and not with the backing of any authority or society. It is provisional in the expectation that it can be improved by criticism and new research findings. It is a comprehensive summary of the development of the specialty, its core knowledge and recommended investigations and interventions. It is concise (under 6,000 words, taking less than an hour to read) in order to increase readership and facilitate translation. No attempt has been made to parade the evidence for these suggestions, because the document would have been too long to translate, and for many to read. Instead, drafts were circulated for criticism by those included in the authorship, resulting in a consensus (finalised by the three principal authors), providing a framework to guide service provision, clinical practice and research. The full list of authors, from 33 nations, is given in the postscript. They include mother-infant (or parent-infant) and perinatal adult or child psychiatrists and those with a special interest; mother-infant, perinatal and forensic psychologists; psychiatric nurses; the founders of Postpartum Support International and the Association for Postnatal Illness; representatives of social work and obstetrics and the management of these services, and research scientists working in the field.