This study investigated the extent to which new reading comprehension proficiencies may be required when adolescents read for information on the Internet. Seventh graders (N = 109) selected from a stratified random sample of diverse middle school students completed a survey of topic-specific prior knowledge and parallel scenario-based measures of online reading comprehension. Standardized reading comprehension scores were also collected. Results indicated performance on one measure of online reading comprehension accounted for a significant amount of unique variance in performance on a second measure of online reading comprehension after controlling for standardized test scores of offline reading comprehension and topic-specific prior knowledge. Furthermore, there was an interaction between prior knowledge and online reading comprehension, such that higher levels of online reading comprehension skills may help compensate for lower levels of topic-specific prior knowledge when adolescents are asked to locate, critically evaluate, synthesize, and communicate information using the Internet. The author discusses a series of alternative interpretations of the data as well as their implications for literacy theory and research. (Contains 2 figures and 2 tables.)