Although it has been widely accepted that the noun phrase accessibility hierarchy (NPAH) in Keenan and Comrie (1977, 1979) plays a significant role in the acquisition of relative clauses, the interpretations of this correlation vary. To test the role of the NPAH in Korean learners` acquisition of English relative clauses, we conducted three experiments: a sentence combining test, a computerized reading comprehension test, and a sentence combining test checking animacy effects. Our results were consistent with the predictions made by the NPAH. In addition, contrary to the argument made by Traxler et al. (2002), we confirmed that the NPAH effects cannot be substituted with animacy effects, but are more likely correlated with the processing difficulties encountered among relative clause types. (Kyungpook National University)