In the UK and other countries roadside masonry parapet walls are commonplace. Such walls were, however, generally not designed from the outset to resist out-of-plane impact loadings from highway vehicles. The consequences of an impact can obviously be severe, particularly in the case of railway overbridges. Following a programme of experimental impact tests performed in the 1990s on unreinforced masonry walls, this paper describes an investigation of the performance of reinforced masonry walls, tested under carefully controlled conditions in the laboratory. A total of 17 tests were performed on unreinforced and reinforced walls. The reinforced walls incorporated either bed joint reinforcement or one of two different types of drilled-in reinforcement. Whereas the bed-joint reinforcement was found to be largely ineffectual, the drilled-in reinforcing systems were found to be capable of enhancing the ability of plain masonry walls to resist impacts, ensuring a ductile response to the applied transient loading. The effect of drilled-in reinforcement on the resistance of walls with low-strength mortar was found to be particularly dramatic, changing the response from that of penetration and disintegration of the masonry to ductile behaviour, with the integrity of the wall maintained and only minimal wall displacement.