This study examines the effects of foreign students' knowledge of a particular academic area on their comprehension of written texts in English. The students' university majors or areas of study included administration and finance, engineering, math and/or physics, and liberal arts. In two studies, the students performed tasks related to texts in engineering, administration and finance, and general material. In the third study, students took different versions of a standardized English language study skills test. In the first two studies, consistent differences in comprehension were found between groups and among texts. Some slight discrepancies with expected results were found in the third study, but overall the three studies confirm the importance of prior knowledge in reading comprehension in English as a second language. (MSE)