Little is known about what guides children in their acquisition of grammatical categories. This paper investigates how semantic knowledge could be involved in discovering these categories, thus confronting two competing hypotheses: are semantic categories innate, or are they developed in a piecemeal fashion? We tested for regular associations between basic semantic dimensions and the development of the founding categories of noun and verb. Six perceptually based semantic dimensions (Parisse and Poulain, 2010), shared by nouns and verbs but potentially distinctive, are coded in the productions of three children aged 1;06 to 2;06. Our results suggest that semantic dimensions do not offer an entry into the early differentiation of noun and verb categories.