Objective: Special observation is a seriously invasive and resource intensive intervention. It is necessary to scientifically conceptualise this measure for further investigations and practice. Methods: Evolutionary concept analysis. Results: The identified antecedents, attributes and consequences of special observation range between control and therapy as well as the safety of patients and the coverage of the professionals. Antecedents comprise of legitimisation (indication, assessment, prescription), resources (internal guidelines, architectural structures, information) as well as context factors (security needs, personal attitudes). The identified attitudes are organisation (qualification, shifting carers, length, place), intervention (relationship, re-assessment, transparency) as well as the field of tension between control and therapy. The consequences consist of side effects (patients, nurses, resources) and conflicts (ethical dilemmas, role conflicts). Conclusion: Society and discipline have influenced the concept over time and a distinction between the custodial and controlling pattern versus a therapeutic approach is recommended.