The compulsory use of lap/sash seat belts has improved crash protection of car occupants but belts do not always provide absolute protection and although they assist in prevention of severe injury to head and thorax, they can produce other injuries in some crashes. An investigation of anatomical aspects of lap strap fit is reported. Radiographic techniques were employed to determine the relative dispositions of the bony pelvic structure and of the seat belt. Examinations of surface anatomy were used to demonstrate the effects of changes in seat belt geometry. It is concluded that lap strap fit can be assessed from surface anatomy by a simple technique; that the most satisfactory seat belt geometry requires a lap strap to be steeply inclined when viewed from the side; that the existing ADR specification of seat belt geometry should be revised on the basis of locations of anatomical landmarks.