We investigated whether infants are sensitive to visual trajectory forms by using trajectories that were spatially but not temporally symmetric. We also tested whether the infants were sensitive to the dynamics underlying these trajectory forms. 8-month-old infants were habituated to a videotaped event run either forward or reversed in time, and then switched to the same event run in the opposite direction, reversed or forward respectively. Infants dishabituated when switched to the novel direction in time, indicating sensitivity to the form of the trajectory. However, the infants were not sensitive to the underlying dynamics as revealed by equivalent habituation and dishabituation times for forward (normal) and reversed (impossible) events.