The paper presents the findings of the monitoring of the long-term deflections of three bridges which were retrofitted with external post-tensioning. The emphasis is on the effect of the additional post-tensioning on the bridge behaviour in the years following the retrofit. The bridges are highway prestressed concrete box-girder bridges built by the balanced cantilever method and retrofitted with additional exterior post-tensioning cables for deflection control. It is shown that external posttensioning can be a successful retrofitting technique for bridges with serviceability limit state problems. The reported examples also highlight the value of long term monitoring of concrete bridges for the assessment of bridges, and for the design of retrofitting scheme.