This study examines the receptive vocabulary size of Japanese EFL learners of the ages from 16 to 19, and describes characteristics and differences according to their school year, overall English ability, and whole vocabulary size. The results showed that the average vocabulary sizes of students of the first, second and third years in a college of technology are about 2370, 2612, and 3417 words. It showed also that the average vocabulary size of the third graders is comparable to that of well-motivated students of a public high school, and that there is no statistically significant difference in the annual increase in the vocabulary size between the learners whose overall English skill is low and those who are at a higher level.