We report on two patients with unilateral hyperkinetic movement disorders associated with contralateral hemiparesis and ipsilateral basal ganglia lesions. The first patient, a 47-year-old woman, had a low-grade astrocytoma located in the right basal ganglia extending into the subthalamic area and the cerebral peduncle. She presented with left hemiparesis, right hemichorea, and intermittent right-sided tremor at rest. The second patient, a 85-year-old woman, had hypertensive hemorrhage to the right posterior basal ganglia, the posterior limb of the internal capsule, the lateral thalamus, and the subthalamic region with accompanying intraventricular bleeding. She developed right-sided transient hemichorea-hemiballism. A videotape illustration of one of the patients is provided. The literature on the rare occurrence of ipsilateral hemichorea-hemiballism is discussed and possible pathomechanisms are reviewed. We postulate that hemiparesis contralateral to basal ganglia lesions might have a conditioning effect on the appearance of ipsilateral dyskinetic movement disorders.