ABSTRACT  An implicit assumption in foreign language reading material preparation has been that new-word density should be kept low. The original hypothesis of the study reported here was that there would be a maximum facilitating density with respect to vocabulary acquisition and other factors. Several sources had suggested that a density of one new word per thirty to thirty-five known words might be the desirable maximum. Seven new-word densities ranging from one new word per 150 known words to one per fifteen known words were investigated. Results failed to support the original hypothesis: vocabulary learning continued to increase through the full range of densities investigated, and no consistently significant effects of new-word density on comprehension, reading time, or student ratings of the material's difficulty or enjoyability were found.