This chapter deals with the comprehension processes. It discusses some of the literature on the development of the capacity to comprehend metaphors in children. The chapter addresses some theoretical mechanisms whereby the comprehension of metaphor might take place. It provides the effects of metaphor on learning, particularly with respect to the role of metaphors in text. The phenomenon of metaphor is much more complicated than it might seem. Several theories of metaphor have been proposed since the time of Aristotle to modern times. Many of the experimental studies designed to investigate the comprehension of metaphors in children are confounded because the investigators failed to control for world-knowledge. Some metaphors are metaphors only because the contexts in which they appear force a metaphorical interpretation. Metaphor is more than a linguistic and psychological curiosity. Metaphors are like jokes; good ones can be very successful, but bad ones can be disastrous.