The article points out the most striking problems of the Czech codification of capitalisation in toponyms in which disagreement with onomastic theory is displayed. The first part of the paper focuses on capitalisation in prepositional toponyms, mostly street names. According to the new codification, valid since 1993, in prepositional toponyms the word following the preposition should be always written with a capital letter. This rule has not been respected by some local authorities (including the Prague municipal authority) or by the Czech Office for Surveying, Mapping and Cadastre. The second part, forming the core of the paper, argues against the theory of the so-called generic and proper-name component of a naming unit which is used for explaining the principles of codification of proper names’ capitalisation. According to the author, this theory is in contradiction with onomastic principles. The last (and shortest) part deals with capitalisation in toponyms containing two subsequent adjectives. The character of the paper is polemical; it points at the inconsistency of the current codification of proper names’ capitalisation in Czech, as well as recent treatises on this topic. The aim of the paper is not to provoke an instant and impetuous codification change, but to stimulate a discussion on this topic.