Abstract
A longitudinal case study investigated if Korean learners of English who passed their critical periods for L2 learning could successfully acquire grammatical knowledge implicitly through a repetitive study-test sequence. During the training session, four subjects were exposed to grammatical sentences embedded with target grammars. They read the sentences by self-paced reading, and took immediate grammaticality judgement task without any explicit feedbacks. After four consecutive days of training, they took delayed tests to examine their three types of knowledges: explicit knowledge, implicit knowledge, and lexical processing knowledge. The result showed that mere exposure to grammatical sentences without any explicit explanation, learners could acquire L2 grammar knowledge, and the knowledge had survived even after a month since the experiment finished.