Symbols, encryptions and codes are a way to hide sensitive or highly personal content in diaries. This kind of private language is an important feature of diary practise, regardless of time and place, but it has barely been studied yet. This article highlights symbols that designate masturbation in diaries of the mid-17th century until the first half of the 20th century. These symbols are interpreted not as ‘silence,’ but as disguising, narrative strategies. They form an integral part of the text and should be studied as such. The central question is how authors by employing disguising strategies (such as symbols) in diaries position themselves within and against public discourse on masturbation. The main body of sources consists of six diaries from different national contexts. The discourse against masturbation which developed from the beginning of the 18th century was an international (Western) affair. In medical treatises and pedagogical manuals for parents, masturbation became a ‘total illness’: a life-threatening activity that would lead to near-certain (and gruesome) death. Diary writing functioned as a medium to register and control this secret vice but the diaries also show ways to change or resist the dominant discourse. The symbols for masturbation re ect some crucial aspects of diary writing: the diary as a memory device and a medium of registry and control of bodily processes, in which private experience is connected to public discourse.