This paper has two goals. The first is to pursue and further motivate some ideas on the status of the notion feature class in phonological theory. The second is to explore the phenomenon of place assimilation. These goals are brought together in an exploration of facts involving nasal place assimilation to complex segments: assimilation in such cases is often partial in the sense that only one articulator of the complex segment spreads under a general process of place assimilation. As we will see, partial assimilation of this sort bears in an important way on our understanding of feature classes.