The paper investigates the potentially distorting impact of grammaticalization on grammar through the analysis of different types of synchronic form-meaning mismatches which may result from the expansion of a grammaticalization process. Grammaticalization may induce mismatches as a consequence of the development of abnormal structures or new constructions incompatible with the general patterns of the language. Mismatches may also be due to an unchanged residue of grammaticalization, which may derive either from inertial resistance or from a superordinate restriction which prevents the grammaticalization wave from extending to specific domains. Finally, mismatches may also be the result of language contact, either by making use of alternative devices of a foreign origin or by preventing the grammaticalization of native structures due to the introduction of ready-made borrowed constructions.