A Case Report Form (CRF) is a paper or electronic questionnaire specifically used in clinical study research. The case report form is the tool used by the sponsor of the clinical study to collect data from each participating patient. All data on each patient participating in a clinical study are held and/or documented in the CRF, including adverse events. The sponsor of the clinical study develops the CRF to collect the specific data they need in order to test their hypotheses or answer their research questions. The size of a CRF can range from a handwritten one-time ‘snapshot’ of a patient’s physical condition to hundreds of pages of electronically captured data obtained over a period of weeks or months. (It can also include required check-up visits months after the patient’s treatment has stopped.) The sponsor is responsible for designing a CRF that accurately represents the protocol of the clinical study, as well as managing its production, monitoring the data collection and auditing the content of the filled-in CRFs.