What makes reading comprehension difficult, and how can we assess comprehension effectively? Before we attempt to answer such questions, we need to outline the nature and characteristics of comprehension processes, for comprehension is not a single unitary process. Instead, it requires the delicate interaction of several component processes that integrate information from the page that the student is reading with his or her background knowledge and experience, subject to a multitude of contextual constraints. Linguists and logicians have analyzed texts for a long time. Psychologists, on the other hand, have been less interested in the texts themselves and their structure and meaning, but in the processes involved to transform the meaning on the page into meaning in the mind. Although models of comprehension differ in many (important) details, we believe that there is an emerging consensus on a general framework. For concreteness, we focus here on our own work (Kintsch, 1998; Kintsch & van Dijk, 1978). The model we describe is a model of adult, fluent reading comprehension. Educators are primarily concerned with students who are learning to read; students, almost by definition, are not fluent readers. So why bother with a model of adult, fluent reading comprehension? There are two strong reasons for doing so. First, if we try to transform beginning readers into fluent readers, it is important to know the characteristics of the goal state that we want to achieve. Second, the striking contrast between the performance of fluent readers and the struggles of beginners must be the starting point for how instruction in read-ing comprehension should be conceptualized.