["This study compares self-paced timing performance (cross-sectionally and longitudinally) between participants with prodromal Huntington's disease (pr-HD) and a comparison group of gene non-expanded participants from affected families (NC).", 'Participants (747 pr-HD: 188 NC) listened to tones presented at 550-ms intervals, matched that pace by tapping response keys and continued the rhythm (self-paced) after the tone had stopped. Standardized cross-sectional and longitudinal linear models examined the relationships between self-paced timing precision and estimated proximity to diagnosis, and other demographic factors.', 'Pr-HD participants showed significantly less timing precision than NC. Comparison of pr-HD and NC participants showed a significant performance difference on two task administration conditions (dominant hand: p < .0001; alternating thumbs: p < .0001). Additionally, estimated proximity to diagnosis was related to timing precision in both conditions, (dominant hand: t = -11.14, df = 920, p < .0001; alternating thumbs: t = -11.32, df = 918, p < .0001). Longitudinal modeling showed that pr-HD participants worsen more quickly at the task than the NC group, and rate of decline increases with estimated proximity to diagnosis in both conditions (dominant hand: t = -2.85, df = 417, p = .0045; alternating thumbs: t = -3.56, df = 445, p = .0004). Effect sizes based on adjusted mean annual change ranged from -0.34 to 0.25 in the longitudinal model.'] Does self-paced timing detect and tracks change in prodromal Huntington disease?