Aim: To study the prevalence of posttraumatic stress in parents after an acute admission to a paediatric intensive care unit (PICU) and to determine risk factors for the development of posttraumatic stress. Methods: Parents completed posttraumatic stress questionnaires three months after their child's discharge. This questionnaire measures both symptoms of posttraumatic stress disorder (PTSD) and enables determination of the full psychiatric diagnosis of PTSD. Medical and demographic data concerning their child were gathered from physical evaluations three months after discharge. Of 250 eligible families, 144 (57.6%) participated in this study. The questionnaires were completed by 140 mothers and 107 fathers. Results: More than three-quarters of the parents experienced persistent symptoms of PTSD. In 21 mothers (15.0%) and 10 fathers (9.3%), the full psychiatric diagnosis of PTSD was determined. In six families, both parents had PTSD. Furthermore, a significant positive correlation was found between symptoms of PTSD of the mothers and the fathers. No obvious medical risk factors could be distinguished. Conclusion: The unexpected admission of a child to a PICU is a stressful event associated with parental posttraumatic stress. Treatment should not end after discharge. Follow-up care is warranted and research should be focused on prevention of these symptoms. © 2007 The Author(s).