This book is the first monographic study on subtitles for the deaf and hard of hearing from a multidisciplinary perspective, from engineering to philology. The book departs from studies, analyses, tests, validations, resulting data, and their application from the nation-wide research on accessibility and usability of subtitles carried out in Spain. Tests and further analysis were carried out paying attention to users' hearing profiles, the many formal features of subtitles - size, font, colour, position, etc. -, and the syntax of the subtitle. The book also contains articles which discuss present and future research on subtitles for the deaf and hard of hearing carried out in Canada and across Europe: Belgium, Denmark, Italy, Poland, Spain, and UK. It provides an outlook for the implementation of the European Guidelines on media accessibility.