This clinical study of 62 patients with restless legs syndrome and associated anxious-depressed and other clinical states seems to indicate that caffeine is the major etiological factor in the causation of the restless legs syndrome. Anxiety, while modifying the subjective experience of the dysphoric sensation of restless legs, is not a causative factor. Caffeine is responsible for the increased nervous system arousal as well as for the direct peripheral contractile effect on the striated muscle. This arousal is often reflected psychologically in anxiety and sometimes depressive manifestations, insomnia, heightened proprioceptive awareness and physiologically in the toxic sensory experience of restless legs associated with increased neuromuscular reactivity which may include myoclonus and myokomia.