Abstract The aim of this paper is to show to what extent the Mainland Scandinavian languages Danish, Norwegian and Swedish differ with respect to the forms used as generic NPs, a topic which so far has not attracted much attention. Based on a survey conducted among native speakers of each language we present the distribution of NP types among generic NPs. The results indicate that the Danish respondents are most consistent in using the definite article generically, while the Norwegian respondents show most variability with respect to which types of NPs are used generically, with Swedish taking an intermediate position. While the use of the definite and indefinite article in the singular varies in Mainland Scandinavian languages, the plural NPs, both bare and definite, are most consistent across languages. We further argue that the observable differences between the languages are a result of different levels of grammaticalization of the definite and indefinite articles in each language, as the use of the definite or indefinite article with generic expressions constitutes the final stage of article grammaticalization. We conclude with a diachronic corpus study of the generic NPs in Old Danish and Old Swedish, to trace the origins of modern variation. The results of this study indicate that the generic use of the definite article in Danish predates that in Swedish, which suggested the definite article grammaticalized earlier in Danish than it did in Swedish and thus became the preferred expression of genericity.