This study examined the second language (L2) acquisition of the Korean plural marker -"tul" by native speakers of English. Seventy-seven learners at four Korean proficiency levels along with 31 native Korean-speaking controls completed five tasks designed to probe for knowledge of particular features and restrictions associated with so-called intrinsic and extrinsic plural-marking in Korean. The results suggest that knowledge of both types of plural developed with increasing proficiency. However, the features associated with the intrinsic plural, which is more similar to the English plural in terms of grammatical function, were more easily acquired than those of the extrinsic (distributive) plural, which requires recruiting the features of a completely distinct morpholexical item from the first language (L1). We also found some developmental evidence for a feature hierarchy in quantified Korean noun phrases, in which the most deeply-embedded featural co-occurrence restriction on intrinsic plural-marking was the latest acquired. (Contains 15 tables, 2 figures and 19 notes.)