Some vehicle manufacturers have recently used lightweight epoxies to fill hollow thin-Walled roof pillars in car subframes to increase their strength and energy dissipation capacity in roll~cver crashes. It is questionable, however, whether epoxy filling is more efficient than increasing the Wall-thickness of a member to improve strength to weight ratios. This paper examines vehicle roof pillars and how their breadth to thickness, b/t, ratio and epoxy filling effects their structural performance under gross bending deformation. A review of theoretical and experimental work carried out to date on void-filled versus hollow sections and an analysis of some typical vehicle roof pillar sections are presented. Conclusions indicate that with present epoxy fillers and roof pillar dimensions, there is no gain in peak strength to weight efficiencies when void-filled sections are compared to their equivalent in weight thicker-walled hollow members, unless compressive strengths of fillers can be increased and/or density reduced.