This study investigated the relationship of collocations to reading and writing skills. Eighty-six Korean university students were given a collocation knowledge test, followed by a reading test; both lexical and grammatical collocations in the collocation test were extracted from the passages in the reading test. Subsequently, the students were given a writing test, and its topic was related to the content of the reading passages; both lexical and grammatical collocations appearing in their compositions were counted based on the classification criteria provided in The BBI Combinatory Dictionaty of English. The findings are as follows. There were no significant correlations between the students' co llocation knowledge and reading ski ll s. However, a significant correlation was found between writing quality and col location use. Good and poor readers were simil ar on average in both grammatical and lexical co llocations, which corroborates the nonsignificant relationship between reading and collocation knowledge. In contrast, good and poor writers showed significant differences in the use of both grammatical and lexical collocations, thus substantiating the significant correlation between writing quality and collocation use. The group difference was more pronounced in grammatical collocations. Across good and poor writers, lexical collocations were used much less than grammatical collocations. Taken together, these results support a need for EFL writers to learn both grammatical and lexical coll ocations to improve writing quality. The results also caution not to overgeneral ize the influence of co ll ocation knowledge on reading performance . •