150 patients with PD in early-moderate and advanced stages of disease (50 in H&Y stage 2, group 1, 50 in H&Y stage 3, group 2 and 50 in H&Y stage 4, group 3) were enrolled. All patients underwent an intensive treatment: 20-minutes treadmill training per day, 6 times a week, for 4 weeks. Treadmill speed was previously set at 2.0 km/h and progressively increased until a maximum of 3.5 km/h, taking always into account the patients' physical abilities. All patients were evaluated at the enrolment and at the end of the 4-weeks treatment. The first evaluation consisted in one-minute walking on treadmill without the use of cues at 1.5 km/h speed, for all patients. The outcome measurements were: the average length of the right step, the average length of the left step, the coefficient of variance of both steps, and the gait cycle.