Abstract: An interlocking building block construction comprising an overlapping masonry block having opposite sides, stepped opposite upper and lower longitudinal faces, and stepped opposite vertical end faces. A plurality of spaced tapered recesses with flat bottom surfaces are located on the upper longitudinal face, and a plurality of correspondingly shaped lugs are formed in the lower longitudinal face. There are two enlarged rectangular openings extending entirely through the block located in the central area of the upper and lower faces between the vertical end faces. A plurality of small apertures are formed in and adjacent to the lugs for receiving pins for interlocking adjacent blocks. Header blocks, pilaster blocks, partition blocks and filler blocks are provided for interlocking assembly with the interlocking building blocks to build walls of a building without the use of grout or cement.