This report reviews recent investigations of the effects of treadmill training (TT) on the gait of patients with Parkinson's disease. A literature search identified 14 relevant studies. Three studies reported on the immediate effects of TT; over-ground walking improved (e.g., increased speed and stride length) after one treadmill session. Effects persisted even 15 min later. Eleven longer-term trials demonstrated feasibility, safety and efficacy, reporting positive benefits in gait speed, stride length and other measures such as disease severity (e.g., Unified Parkinson's Disease Rating Scale) and health-related quality of life, even several weeks after cessation of the TT. Long-term carryover effects also raise the possibility that TT may elicit positive neural plastic changes. While encouraging, the work to date is preliminary; none of the identified studies received a quality rating of Gold or level Ia. Additional high quality randomized controlled studies are needed before TT can be recommended with evidence-based support.