Despite the benefits related to ambulatory surgery such as cost reduction due to lack of accommodation and patient satisfaction due to early home return, it may not lead to these expected benefits. Indeed, this kind of practice can increase responsibility for the person being treated and his or her relatives. It is therefore essential to inform them as well as possible to obtain their adherence to the proposed care protocol. Nevertheless, patients’ failures to comply with preoperative instructions or the non-attendance of the patient may result in late cancellation of the scheduled surgery. In order to reduce this kind of dysfunction, the Assistance Publique-Hôpitaux de Paris (APHP) uses a reminder system by Short Message Service (SMS). This study is a descriptive cross-sectional multicenter study that focuses on outpatients’ lived experiences of their preoperative preparation and information. It aims to collect patients’ perceptions of their ability to follow preoperative instructions received by SMS the day before an operation performed for ambulatory surgery, according to their level of health literacy (HL) and preoperative anxiety. Indeed, poor communication between patients and doctors can contribute to preoperative anxiety, while low health literacy (LHL) can lead to poor understanding of preoperative preparation instructions. Therefore, it seems important to take these 2 criteria into account in this study. This research is designed to interview outpatients undergoing ambulatory surgery in the establishments of APHP. A self-questionnaire will be used for this purpose. The choice of this institution is justified by its decision to use in all care units the reminder of preoperative instructions by SMS. The main outcome is the perception of outpatients with LHL skills regarding preoperative information provided by doctors. French ethics review committee (Comité d’Ethique de la Recherche) of the University of Paris has approved the study protocol (IRB 00012020-14). Results from this study will be disseminated through oral communications and a scientific article in an international peer-reviewed journal. This protocol is registered on researchregistry.com (researchregistry5834). This version number is 1.1 Protocol dated July 22, 2020.