Movement accuracy in normal subjects depends on feedforward commands based on representation in memory of spatial and biomechanical features. Here we ask whether memory deficits in Alzheimer's disease (AD) interfere with movement planning and execution. Nine AD patients and nine age-matched controls moved a cursor to targets without seeing their limb. Starting and target positions were always visible on a screen, while, during movement, cursor position was either visible or blanked. Patients' paths showed discontinuous segments and prolonged movement time; movement inaccuracy, which increased without visual feedback, correlated significantly with scores of disease severity, working memory and attention.