A project was undertaken to evaluate the utility of the penetration test in the Australian Standard devoted to the testing of lightweight helmets for bicycle riders. The project revealed aspects of the protective performance of conventional hard shell helmets and recently developed helmets manufactured entirely from expanded polystyrene foam. Hard shell helmets were found to provide good performance in a range of loading conditions applied to them during testing. In contrast, foam helmets provided very poor resistance to concentrated loads produced during impacts with small, sharp objects but they had greater capacity than hard helmets to withstand distributed loads produced during impacts with flatter objects. The presence of the penetration test in the Australian Standard was determined to have produced the good all round performance of hard helmets which met its requirements. Two tests were proposed as alternatives to the penetration test. They would evaluate foam and hard helmets on equal terms at the cost of abandoning the requirement of helmets to withstand concentrated loads.