This document describes an experimental and numerical investigation into the ability of a bonded-composite doubler to restore the fatigue performance of lap-joints containing multi-site damage. A series of representative lap-joint specimens were fatigue tested to failure in the first row of rivets in the upper skin. Additional damage was introduced to the lower skin at the third row of rivets. In all cases the repaired specimens survived in excess of 200 000 cycles without failure and with no apparent degradation of the doubler. Following this study, two doublers were applied to representative multi-site damage in the lap-joint of a full-scale fatigue-test article. These doublers will be evaluated over the life of the fatigue test.