This book contains the first complete English translation, fully annotated, of the treatise Concerning Frequent Communion, commonly attributed to Sts. Makarios of Corinth and Nikodemos the Hagiorite, the compilers of the Philokalia. This pivotal treatise, by two central figures in the Kollyvades movement, which originated on Mount Athos in the late eighteenth and early nineteenth centuries, addresses a somewhat less well-known corollary issue in Orthodox spirituality, that of frequent Communion. The authors discuss the controversy surrounding a decline in the frequency of Communion in the Christian East, the relationship of that controversy to the Kollyvades movement, and the theological arguments in support of frequent Communion advanced by Makarios and Nikodemos, whose joint authorship of the treatise they endeavor to substantiate.