SUMMARY: This study investigates: 1.The extent to which TOEIC test scores of one ability correlate with test takers' self-assessments of their English abilities across all four skills 2.Whether one English skill (e.g., reading) can be more accurately estimated or predicted using multiple other TOEIC test scores, i.e., listening, speaking and writing For the first point, researchers found significant correlations between self-assessments and TOEIC test scores across all four skills, which provides evidence that TOEIC test scores are valid and meaningful indicators of English-language proficiency. For the second, researchers concluded that more accurate predictions of English-language ability were obtained when multiple TOEIC test scores were used. This can be explained by a conceptualization of language proficiency in which language knowledge (e.g., grammar, vocabulary) is utilized across language skills, and demonstrates that four-skill assessment can be used to measure any single language skill even more accurately. (This outcome is consistent with the results of the externally conducted study The Incremental Contribution of TOEIC Listening, Reading, Speaking and Writing Tests to Predicting Performance on Real-Life English Language Tasks.)