I will examine phonological cues to grammatical class in English, and implicit knowledge of such cues. In particular, I will describe experiments showing that both native and nonnative English speakers can learn such patterns, and that knowledge by nonnative speakers is not correlated with their age of arrival in an English speaking environment. I will discuss implications of this lack of "sensitive period" effects for our understanding of language acquisition. In the next part of the talk, I will address the question of how much information about grammatical class can be squeezed out of phonology, using connectionist models as an exploratory device. Finally, I will discuss implications of this research for language acquisition, production, and innovation.