Elevated homocysteine (Hcy), prevalent in Parkinson's disease (PD), is potentially a modifiable risk factor for neurologic deterioration. We measured cognitive, affective and motor changes over 2 years in a cohort of people with early PD. Subjects whose Hcy had been elevated (>14 micromol/L, n = 31) at baseline were compared with the rest (n = 66). Overall progression in 2 years did not significantly differ (p = 0.20). Four subjects with elevated and one with normal Hcy had died (p = 0.03). We conclude that hyperhomocysteinemia does not predict significantly worse progression over 2 years in early PD. The data raised the possibility of higher mortality, but the number of deaths was small.