Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteers was performed with a fully automatic motion analyser. The recording included stride parameters for walking velocity, stride length, stride duration and swing time. Maximal amplitudes of rotation of the hip, knee and ankle were also recorded. The analysis was performed for the PD's patients before and after L-Dopa intake. All the patients walked with and without transversal stripes on the floor. The contrasting white lines were 45 cm apart. After medication, the stride length, the velocity and the swing phase duration were significantly increased. The movements around the hip, knee and ankle joints that were initially reduced, poorly increased after L-Dopa intake. When stripes were placed on the floor, no significant changes occurred for the overall group of patients. Seven parkinsonian patients did improve with visual guidance, increasing their stride length and their speed. Some rotations of hip and knee were also influenced by stripes. This sub-group of patients was characterized by older age, a slower walking velocity, a smaller stride length and a shorter swing time. We correlated the sensitivity to visual cues to the defect of the visual contrast sensitivity that has been established in PD by several recent works. Locomotion on the transverse lines might have produced a motion perception at a rate determined by the speed of the patient. For appropriate intervals between stripes, one can hypothesise that the resulting visual stimuli belonged to a range of spatio-temporal frequencies that are decreased in patients with PD.