Both seat belt slack and anchor location are known to affect occupant excursion during high speed frontal collisions, but their effects have not been studied at moderate collision severities. The goal of this study was to explore how seat belt slack and anchor location affects occupant kinematics and kinetics in moderate frontal collisions. A Hybrid III dummy was seated on a programmable sled and exposed to frontal collisions with a speed change of 17.5 km/h. The seat belt was adjusted either snugly or with 10 cm slack (distributed 60/40 between the shoulder and lap portions) and the anchor location was varied by adjusting the seat position either fully forward or aft (seat travel = 13 cm). Accelerations and displacements of the head, T1, and pelvis were measured in the sagittal plane. Upper neck loads and knee excursions were also measured. Five trials were performed for each of the four combinations of belt adjustment (snug, slack) and anchor location (seat forward, seat aft). For each trial, kinematic and kinetic response peaks were determined and the combined data were compared using repeated-measures ANOVAs. Peak excursions, accelerations and loads varied significantly with both seat belt slack and anchor location. Seat belt slack affected more parameters and had a larger affect than anchor location on most peak dummy response parameters. Head excursions increased a similar amount between the snug/slack belt conditions and the aft/forward anchor locations. Overall, horizontal head excursions increased from 23 cm in the snug-belt, rearward-anchor configuration to 33 cm in the slack-belt, forward-anchor configuration. These results showed that analyses of occupant excursion need to consider potential sources for seat belt slack and account for differences in seat belt anchor locations.