Abstract: A modular reamer for use in a wellbore comprises an uphole end member, a center member, and a downhole member, with reamer sleeves that removably slides over a sleeve mounting portion of the center member or one of the end members, and are held between the end members and the center members when assembled into a downhole tool. The reamer sleeves may be positioned at any desired rotational angle relative to each other and are prevented from rotational movement relative to the center member by spines or keys formed on the mating surfaces of the reamer sleeves and corresponding members of the modular eccentric reamer.