The authors evaluated motor, behavioral, and cognitive functioning over a 3-year period in 33 presymptomatic carriers for Huntington's disease and compared them with 73 noncarriers. Investigators blind to the participant's gene status utilized the Unified Huntington's Disease Rating Scale (UHDRS) and performed an extensive neuropsychological assessment (global cognitive, memory, language, psychomotor). Successive evaluations of motor and behavioral patterns showed inconsistencies. The rate of cognitive changes in carriers was similar to that in noncarriers. Commonly used tools are inadequate for detecting markers in preclinical Huntington's disease, limiting the design of therapeutic trials. Research should focus on tracking suitable endpoints combining clinical markers and biomarkers that change linearly with disease progression.