The present study investigates usage of English futures, will and be going to, by Korean EFL learners and American native English speakers. The examined usage data are extracted from the native speaker corpus, the Corpus of Contemporary American English (COCA), and two learner corpora, the Kyungpook National University (KNU) Student English Learner Corpus-Written (KSELC-W) and the KNU English Learner Corpus (KELC), and compared to determine interlanguage developmental patterns and usage similarities or differences between native speakers and nonnative speakers. In support of existing literature, the findings from the current study reveal that the American native English speakers of COCA significantly overuse both will and be going to in the spoken register compared to the combined written registers. Furthermore, the findings also indicate that although the writing samples of the learner corpora were written during formal EFL education settings, will and be going to usage by the Korean EFL learners closely resemble the usage data of the combined written-all registers of COCA. Finally, semantic analyses show that the advanced learners of KSELC-W use be going to quite correctly with the semantic senses in the present form. In contrast to the learners in Coates (1983), they use be going to to deliver the sense of epistemicity rather than the root intention senses.