We recorded horizontal smooth-pursuit responses to sinusoidal and step-ramp stimuli in 7 patients with unilateral frontal lobe lesions. Five patients had directional smooth-pursuit deficits, all with impairment toward the side of cerebral damage. Ipsidirectional pursuit defects involved pursuit maintenance to sinusoidal targets, pursuit initiation to step-ramp targets, or both. No patient had asymmetry of smooth pursuit according to the retinal hemifield of target appearance. Smooth-pursuit velocities were subnormal in both horizontal directions in 4 patients. The human frontal lobes participate in the initiation and maintenance of smooth pursuit in both directions, with a greater ipsilateral contribution. Of 5 patients with ipsilateral pursuit impairment, 3 had cerebral lesions in the area of the frontal eye field (FEF). These 3 patients also made inaccurate saccades to targets moving away from the side of the lesion, implying that the FEF transmits motion information to the saccadic system. Two patients with ipsidirectional smooth-pursuit defects had cerebral damage that spared the FEF, indicating that other frontal regions also contribute to smooth pursuit.