Measures of glymphatic function could serve as markers of Huntington disease (HD) and its progression, new research has shown. The study included 49 people with mutations in the HTT gene, 35 of whom had clinically manifest HD, and 35 healthy control individuals. Glymphatic function was assessed on the basis of the diffusion tensor image analysis along the perivascular space (ALPS) index, which is a measure of glymphatic flow, and the percentage of perivascular space in the basal ganglia. The ALPS index was lower (indicating reduced glymphatic flow) in people with manifest HD than in people with preclinical HTT mutations, and it was lower in both groups than in healthy participants. The percentage of perivascular space in the basal ganglia also differed between the groups, with the lowest percentage in healthy control individuals and the highest in people with manifest HD, but the ALPS index was a more sensitive measure of changes. The extent of glymphatic impairment correlated with disease burden, suggesting that improving glymphatic function could be therapeutically beneficial.