A group test and individual interviews were used to investigate quantitative and qualitative aspects of students' vocabularies. Subjects for the group test were 144 high-, middle-, and low-ability fourth and sixth graders. Subjects for the interviews were eight high- and low-ability third and fifth graders. The group test consisted of two forms of a 36-item, multiple-choice test comprised of words at various difficulty levels. Subjects received one form of the test as a reading test and the other as a listening test in a counterbalanced fashion. The interviews required subjects to give two meanings for words in isolation, identify two meanings of words presented in two contexts, and distinguish between the meanings of closely related words. An analysis of variance on the group test indicated significant differences due to grade, ability, mode, and word difficulty. However, the difference due to mode was small for both good and poor readers. On the interviews, students did best at identifying multiple meanings in context, and giving multiple meanings for isolated words best distinguished good and poor readers. These and other results are discussed. (Author/GK)