The author describes two cases, the first, a man, æt. 31, who died after fourteen months' illness, with well-marked symptoms of general paralysis. Ten days before death various groups of muscles of the right side of the body (those supplied by lower branch of facial nerve, those of right side of tongue, external abdominal oblique, serratus magnus, biceps cruris, flexors of forearm) were affected by clonus, irregular, with short but distinct intervals; the clonus ceased with sleep, and had no effect on the movement of the muscles. It continued till his death. In the second case, a man, æt. 39, the muscles of face were first affected, and, after a short interval, the right side of body. The movements were arythmic, irregular, and rapid, diminished by movement, increased by an emotion; they ceased in sleep. The pectorals, the abdominal oblique (120 contractions per min.), the extensors of the forearm, and the adductors of the thigh (150 per min.) were all affected. Athetosis, affecting right hand, on one occasion supervened. The clonus later spread to left side of body. During the later stages of the illness they reappeared for a third time. The author points out the relative infrequency of the condition associated with the psychoses. He compares at considerable length the clonus with the allied muscular tremors in chorea in its various forms, and with the group of misclonus associated with epilepsy with a view to establishing the seat of the lesion. This is concluded to be in all these cases probably cortical.