We walk backward on a daily basis, such as when backing away from the kitchen sink or stepping back from a curb as a swiftly moving bus passes. This task may be particularly difficult for individuals with Parkinson's disease (PD) who often fall as a result of moving or being perturbed in the backward direction. The aim of this study was to assess backward walking (BW) in individuals with PD. Both forward walking (FW) and BW were assessed in 78 people with idiopathic PD (H&Y range: 0.5-3) in the ON state, and 74 age- and sex-matched controls. In FW, those with PD had significantly shorter strides, lower swing percents, higher stance percents, and lower functional ambulation profiles than controls. Both groups walked significantly slower and with a wider base of support during BW than FW. Additionally, in BW those with PD walked significantly slower with shorter strides, lower swing percents, and higher double support and stance percents, and lower functional ambulation profiles compared with controls. Those with mild to moderate PD have impaired FW and BW, but differences between those with and without PD are more pronounced in BW.