Improving reading rate can be difficult for poor readers. In this experiment, we investigated the impact of improvement in reading rate on other aspects of reading, including word recognition, decoding, vocabulary, and comprehension. Poor readers in Grades 2 or 4 (N = 123) were randomly assigned to 1 of 3 conditions: practice reading text at their independent reading level (92%-100% word reading accuracy), practice reading text at a difficult reading level (80%-90% accuracy), or an untreated control. Students in practice conditions read aloud to an adult listener who assisted with difficult words. Before, midway, and following 20 weeks of treatment, we assessed improvement in reading rate, word recognition, decoding, vocabulary, and comprehension across conditions and determined the impact of improved rate on comprehension. We found significant differences favoring the treatment groups in rate, word recognition, and comprehension, but not in decoding or vocabulary. We found no significant differences in growth between levels of text difficulty. (Contains 8 tables and 1 figure.)