A power transmission belt for transmitting high loads having an elastomeric looped flat belt portion having a longitudinally extending tensile cord and defining an outer surface and an inner surface, and a plurality of longitudinally extending spaced blocks mounted to the outer and inner surfaces respectively of the flat belt portion. Each block is formed of a core and a fabric wrapped around the core. In one embodiment, the block is secured to the flat belt portion by bolts extending therethrough. The fabric of the blocks may be treated with different materials, such as rubber, synthetic resins, and the like. The core may be formed of an elastomeric material. The flat belt portion may be provided with one or more layers of fabric.