Abstract: A yarn supply apparatus for elastic yarns in knitting machines having abruptly fluctuating yarn consumption. A yarn wheel, around which the yarn to be supplied is wrapped, furnishes the yarn to a yarn store located between a knitting station and the yarn wheel. A closed-loop controller responsive to yarn tension operates the yarn wheel via a low-inertia drive motor. The yarn store is embodied as an essentially straight segment of yarn in the yarn path in which yarn is guided so it can expand freely. The combination of a low-inertia drive motor, a yarn store that utilizes the intrinsic elasticity of the yarn, and a closed-loop controller that monitors the yarn tension by means of a sensor device makes it possible to use the yarn supply apparatus for supplying elastic yarns and to keep the yarn tension essentially constant even when the demand for yarn fluctuates abruptly.