This paper shows that the potential presence of lexical subclasses in a language can be predicted from its parts-of-speech system. The classification of parts-of-speech systems presented in Hengeveld (1992a) is used as a starting point, and the notion of lexical subclass is restricted to those instances that are morphologically based. The investigation of a 50-language sample reveals that the functional flexibility of a lexical class that may occur in various syntactic slots prevents it from manifesting morphologically based subclasses. Lexical classes specialized for certain syntactic positions, on the other hand, do allow morphological subclassification.