The present study investigated the factor structure of a field trial sample of the Test of English as a Foreign Language™ Internet-based test (TOEFL® iBT). An item-level confirmatory factor analysis (CFA) was conducted for a polychoric correlation matrix of items on a test form completed by 2,720 participants in the 2003-2004 TOEFL iBT Field Study. CFA-based multitrait-multimethod (MTMM) analyses for the Reading and Listening sections showed that the language abilities assessed in each section were essentially unidimensional, while the factor structure of the entire test was best represented by a higher-order factor model with a general factor (English as a second language/English as a foreign language ability) and four group factors for reading, listening, speaking, and writing. The integrated Speaking and Writing tasks, which require language processing in multiple modalities, well defined the target modalities (speaking and writing). These results broadly support the current reporting of four scores corresponding to the modalities and a total score, as well as the test design where the integrated tasks contribute only to the scores for the target modalities.