The problems and repair techniques studied were as follows: Problem: Arch ring with insufficient calculated capacity -- Repair techniques: reinforced concrete saddle; repointing; grouting; lining with sprayed concrete; prefabricated liner. Problem: Inadequate foundations -- Repair: mini-piles; underpinning with mass concrete; curtain walls may be combined with grouting and/or stitching of the piers or abutments; invert slabs. Problem: Outward movement of the spandrel walls - Repair: tie bars; and replacing some or all of the spandrel fill with concrete. The County Councils of England and Wales and the Regional Councils of Scotland were asked to provide examples of bridges which had been repaired using the techniques. A total of 180 examples were provided from which a sample of the fifty most suitable was identified for more detailed study. This report provides a useful guide to the effectiveness, the advantages and disadvantages, and the cost of the various repair and strengthening techniques available for masonry arch bridges.