Testing learners' English proficiency is central to university English classes in Japan. This study developed and implemented a set of parallel online receptive aural and visual vocabulary tests that would predict learners' English proficiency. The tests shared the same target words and choices--the main difference was the presentation of the target words. Test results showed that for both the Aural Test (AT) and the Visual Test (VT), average scores from 1,000 to 4,000 of the JACET8000 word list's frequency bands decreased in proportion to word frequency. More detailed analyses highlighted gaps between visual and aural aspects of receptive vocabulary knowledge of frequency of 4,000 and beyond. It further indicated that the aural version of the test was a better predictor of English proficiency. For future directions, we need to develop other sets of the VT and the AT to improve the reliability of the tests, and this is especially important in order to satisfy the needs of educational institutes that demand high accuracy in vocabulary testing. [For the complete volume, see ED578177.]