The purpose of this study was to conduct a replication study of a kindergarten mathematics intervention, ROOTS, delivered within the context of a research base core program. In the study, sixty two classrooms were randomly assigned to treatment (ROOTS) or a business as usual control. All classrooms implemented a research based core program (Early Learning in Mathematics). Participants included 163 treatment students and 145 control students nested within classrooms. Key differences between the current replication study and the original study included geographical region, instructional context, and student initial skill. In contrast to the significant positive effects (Hedges' g values of 0.30 to 0.38) found in the original study, no significant differences were found between the treatment and control conditions. Pretest skills did not moderate treatment effects. Implications for replication research and evaluating intervention efficacy are discussed. [This is the online first version of an article published in "Exceptional Children."]