Research Methodology: We adopted an observational approach using an online Delphi technique, that is a reliable method broadly used to reach consensus among experts on a specific topic. The Delphi technique was chosen because it has several advantages: i) being web-based; ii) allowing communication via email; iii) ensuring participants’ anonymity; iv) guaranteeing the feedback collection through a series of consecutive rounds, in which the questionnaire is progressively revised by experts (round-based methodology); v) permitting impartial analysis and summarization of the data. The study was designed, implemented and coordinated by a steering committee that supervised the process of questionnaire (checklist) development and of experts selection and data collection. Steering Committee: The role of the international steering committee, comprising Carlo Miniussi, Marta Bortoletto, Ettore Ambrosini, Antonino Vallesi, Vincenza Tarantino, Massimiliano Oliveri, Giacomo Koch, Luciano Fadiga, Hartwig Siebner, Ulf Ziemann Alvaro Pascual Leone, Leocani Letizia, Yoshikazu Ugawa, Lefaucheur Jean-Pascal, Alexander Rotenberg, Ines violante, Vera Moliadze, Olga Lucia Gamboa, Abraham Zangen, Andreina Giustiniani and Francesca Burgio was to create a TMS questionnaire to report TMS secondary effects and to select the experts for the Delphi checklist to rate and improve the it. As the first step of the Delphi process, an initial email circulation started within the steering committee to ask each member of the steering committee to suggest a list of items to include in the questionnaire An inclusive list of items was produced based on suggestions derived from the answer of the members. Additionally, the members of the sterring provided a list of authors to be included in the panel of experts for the Delphi. All the members of the steering committee agreed on the list of experts before starting the Delphi. The Delphi procedure started with the recruitment of the group of experts. The main criteria used to recruit the experts were being the first or last author in at least two TMS studies. Potential candidates (n=100) were invited to participate in the Delphi study using the Delphi deicision Aid website. The final expert panel included 100 potential candidates with expertise across a range of backgrounds (general medical practitioner, neuroscientist, biomedical engineer, electrical engineer) and geographical areas. Our aim was creating an instrument (i.e., a questionnaire) that would enable systematic reporting of TMS unintended effects, by gaining consensus among TMS experts. The questionnaire was formulated based on previous evidence and guidelines in the field. The ultimate aim was that the questionnaire could be used by researchers in future studies to enhance both the study’s quality and reporting, so that any study using TMS can use it to report stimulation related sensations.