The long legs, compact body and hanging posture of many harvestmen are unique among terrestrial animals, but no quantitative analyses of locomotion have been conducted to determine if this extreme morphology is associated with novel mechanisms of locomotion. Here we have undertaken a three-dimensional kinematic analysis of running Leiobunum vittatum (Say 1821) using field-by-field analysis of high-speed video. The center of mass of harvestmen was found to undergo vertical and transverse displacements of unprecedented magnitude, but the pattern of displacements was consistent with those predicted by general models of energetic efficiency and dynamic stability of pedestrian locomotion. Because these models assume substantial roles for elastic energy storage in leg elements, elasticity is probably an important component of the locomotor mechanism in harvestmen, and we identify two skeletomuscular elements as possible springs.