Abstract: A modular plastic wall block to be used for forming a retaining wall including a plurality of vertically superimposed courses, each course including a plurality of laterally juxtaposed wall blocks. Each wall block is formed of a wall block frame and an easily replaceable facing panel interconnected by a tongue and groove connection. By rotating the facing panel by 90.degree., it can be used to overly and conceal at least a portion of the top of an uppermost course of wall blocks in the retaining wall. The wall blocks include elements for side-to-side connection enabling juxtaposed wall blocks in each course to be laterally aligned to form a straight portion of a face of a retaining wall, or to be angularly positioned to form concave or convex portions of the face of the retaining wall without the formation of gaps between adjacent wall blocks.