A power transmission belt having a body with a length, an inside, an outside, and laterally spaced sides. The body has a bonding rubber layer in which elongate load carrying cords are embedded to extend lengthwise of the body. The body has a first layer on the inside of the bonding rubber layer in which a plurality of laterally spaced ribs are formed extending lengthwise of the body, and a second layer on the outside of the bonding rubber layer in which a plurality of laterally spaced ribs are formed extending lengthwise of the body. The bonding rubber layer has a sulfur-crosslinked rubber composition including an ethylene-&agr;-olefin elastomer. At least one of the first and second layers has a crosslinking product that is an organic peroxide-crosslinked rubber composition including an ethylene-&agr;-olefin elastomer.