A chainsaw comprises a main body (1), a motor housed within the main body, the motor being drivably connected to a sprocket drive shaft (6), and a guide bar/saw chain assembly (4). The assembly (4) comprises a guide bar (7, 8), a saw chain (12) and a sprocket drive wheel (5). The guide bar has first and second guide bar portions (7, 8) telescopically connected together, and the sprocket drive wheel (5) is associated with the second guide bar portion (8). The saw chain (12) is in drivable engagement with the sprocket drive wheel (5) and passes around the peripheries of the first and second guide bar portions (7, 8). The sprocket drive wheel (5) is in drivable engagement with the sprocket drive shaft (6). The assembly (4) is movable between a first, non-operative position in which the first and second guide bar portions (7, 8) are positioned so that the saw chain (12) is not tensioned, and a second, operative position in which the first and second guide bar portions are positioned so as to tension the saw chain.