The topic of word classes remains curiously under-represented in the sign language literature due to many theoretical and methodological problems in sign linguistics. This article focuses on language-specific classifications of signs into word classes in two different sign languages: German Sign Language and Kata Kolok, the sign language of a village community in Bali. The article discusses semantic and structural criteria for identifying word classes in the target sign languages. On the basis of a data set of signs, these criteria are systematically tested out as a first step towards an inductive classification of signs. Approaches and analyses relating to the problem of word classes in linguistic typology are used for shedding new light on the issue of word class distinctions in sign languages