Abstract: A cylinder lock-key-combination includes a lock cylinder, a cylinder housing (2) and a cylinder plug (3) provided with a key slot (3a) and a row of tumblers (5). The tumblers (5) and associated key (4) present mutually adapted engaging and receiving members which function to forcibly guide movement of the tumblers in two opposite axial directions as the key is inserted into the lock. For instance, the pin tumblers (5) include a circular flange (5a) and a side surface of the key (4) includes a groove (4b) which extends along the length of the key and whose width varies so as to accommodate the flanges of the rotatable or twistable tumblers. Alternatively, the tumblers are provided with a groove or a waisted portion and the key is provided on a side surface thereof with a rail which engages in the groove or waisted portion.