Letters to the editor are brief texts that are published in a special section of medical journals. There are two types of letters to the editor: the observation and the comment. The former presents original work, while the latter constitutes criticism on work already published in the same journal. Although short, letters to the editor require as much effort and discipline in writing as, indeed, any other manuscript. Clarity and brevity should be their principal values. It is also important to comply with the journals' instructions for correspondence. Thus, eloquent letters to the editor may promote knowledge and enable fruitful exchange of ideas.