This study is to probe into the quantitative aspects of in vocabulary in the first volumes of the major three senior high (SH) school English textbooks and the major three vocational high (VH) school English textbooks. Not only the vocabulary lists, but also the unlisted new words in the related sections which are categorized into 22 corpora are explored and compared in terms of the size of new words, the consistency between junior high school (JH) vocabulary lists and SH/VH textbooks, the new-word density, and the frequency of word exposures. In addition to the six commercial SH/VH English textbooks from three major publishers (Far East, Lungteng, and Sanmin), four JH word lists are included: two word lists of the old centralized Junior High School Required (Word-JHA) and Elective (Word-JHB) English Course by the National Institute for Compilation and Translation and two new word lists of 1,000 productive vocabulary (Word-JH1000) and 1,000 receptive vocabulary (Word-JH2000) by the MOE. The major findings of this study are as follows: 1. The word size, particularly the unlisted new words, is big. For those SH students who learn both Word-JH1000 and Word-JH2000, they face 9.05%~13.36% of unlisted new words in reading sections and encounter 17.92%~22.55% of unlisted new words in the whole textbooks. For those VH students who learn both Word-JH1000 and Word-JH2000, they face 5.77%~12.62% of unlisted new words in reading sections and encounter 16.05%~21.90% of unlisted new words in the whole textbooks. 2. Even though the new JH vocabulary lists (Word-JH1000 & Word-JH2000) provides a larger proportion of overlapping with the 22 SH/VH corpora than the old JH vocabulary (Word-JHA & Word-JHB), the consistency of vocabulary between JH and SH/VH is not adequate enough to reach the ¡§all-or-nothing threshold¡¨ (80% known words in a certain text). 3. Both SH and VH textbooks are too dense with new words to reach the ¡§probabilistic threshold¡¨ (95% known words in a certain text), the density index of an efficient textbook for the first year. 4. The frequency of word exposures is too low to be well-learned (more than 80% beneath the six-time threshold; more than 40% are one-timers). The findings have some pedagogical implications regarding the suggestions for the policy-makers, publisher, JH/SH/VH teachers and students.