This study investigated poor readers' use of prior knowledge in reading by comparing good and poor readers' recall of familiar and unfamiliar text. Thirty-one third graders and thirty-one fifth graders, reading on a third grade level, and twenty fifth graders, reading on a fifth grade level, read and orally recalled two third grade expository passages, one on a familiar topic and one on an unfamiliar topic, which were very similar in structure. Both fifth grade groups recalled more than the third graders on the familiar passage. The fifth grade good readers recalled more than the poor readers and third graders on the unfamiliar passage. All groups recalled more on the familiar than unfamiliar passage, but the poor readers' mean difference score between the two passages was greater than the other two groups' mean difference scores. These findings suggest that poor readers' comprehension, in particular, suffers when their use of prior knowledge is restricted, as when reading unfamiliar material. Also, it appears that poor readers can do an adequate job of comprehending if given familiar material to read on an appropriate level.