This study aimed to provide information about the quality of the evidence on reading fluency instruction for at-risk students and students with reading/learning disabilities as a way to evaluate whether an instructional strategy is evidence-based and has potential for classroom use. An extensive search process with inclusion and exclusion criteria yielded a total of 18 studies to be included in the present study: 12 group design studies and six single-subject design studies. The quality indicators proposed by Gersten et al. ("Except Child" 71:149-164, 2005) and Horner et al. ("Except Child" 71:165-179, 2005) were applied to evaluate the quality of selected fluency intervention studies. Results revealed that (a) most group design studies provided little information about the intervention and agent for the comparison group, (b) internal and social validity were not clearly stated in single-subject design studies, and (c) procedural fidelity in assessment and intervention implementation was inadequately addressed in both group design and single-subject design studies. Lack of methodological rigor, which hampers determinations of the effectiveness of fluency instruction, the current status of intervention studies, and future directions are discussed.