Two studies were conducted to examine the effects of Tier 2 and Tier 3 mathematics interventions on students with mathematics learning difficulties. In the first study, the work of Bryant et al. was replicated and expanded upon by documenting the sustained effects of a Tier 2 mathematics intervention on mathematics performance by second graders. In the second study, the Tier 2 intervention was intensified to a Tier 3 intervention through increases in two instructional features: group size and dosage. The results of the first study showed that the Tier 2 intervention improved mathematics performance for the majority of student participated in the study, and the effect of the intervention was sustained for the majority of students who responded to the Tier 2 intervention. The results of the second study showed that intensified Tier 3 intervention that involved one-on-one instruction and extended time for daily lessons may benefit students who have persistent difficulties with learning mathematics.