This study aimed to assess the independent associations of serum levels of vitamin B12 and plasma concentrations of homocysteine with gait speed decline in participants 50 years or older from The Baltimore Longitudinal Study of Aging, N=774.Gait speed (m/s) was assessed using the 6-meter usual pace test. Vitamin B12 and homocysteine concentrations were collected using standard clinical protocols. Elevated homocysteine concentrations were associated with decline in gait speed after adjustment for covariates.