The mathematical symbols in Z have caused problems for users and tool builders in the past—precisely what is allowed? ISO Standard Z answers this question. This paper considers the Z notation at the level of the individual characters that make up a specification. For Z authors: it reviews the internationalisation of Z, discusses what characters can be used in forming names, and summarises the changes made to LATEX mark-up in ISO Standard Z. For Z tool builders: it explains the sequence of processing that is prerequisite to the lexing of a Standard Z specification, and considers in detail the processing of LATEX mark-up.