Kinesin-1 is a walking machine that takes ~8 nm steps along microtubules. Some aspects of the molecular mechanism of walking are now clear, but many are not. In the present paper, we discuss currently controversial points, focusing on the pathways by which kinesin takes occasional backsteps. Backsteps represent failures of the forwards-biasing mechanism. By studying the mechanochemistry of backstepping, one can learn much about the underlying molecular mechanisms responsible for forwards directional bias in the walking action.