The International Classification of Functioning, Disability and Health (ICF) is considered to be a useful tool to overcome differences among different health professionals and to facilitate a common understanding of the patient and of what constitutes care. Three lists of ICF intervention categories for internal medicine have been developed. The next step of the development process is to address their content validity. The data for this study were derived from 300 clinical records. The study was conducted as a retrospective cross-sectional multicentre study in Switzerland. It was performed using convenience samples of records of patients with internal medicine conditions. The validation process enabled the identification of 36 ICF intervention categories in the acute, 41 in the rehabilitation and 38 in the long-term contexts. The developed lists might help define the core competencies of the profession of physiotherapy. These intervention categories are available for intervention documentation in a standardized common language, the ICF, and they offer the possibility of responding to the health-political demand for transparency regarding services offered by health care providers.