Ply-drops must be taken into account in the design of composite structures due to the initiation and propagation of delaminations at ply-drop locations. This damage mode is experimentally investigated in tension-tension fatigue and the fatigue delamination growth rate is measured for two (external and internal) ply-drop geometries. It is found that the fatigue delaminations grow at a constant rate. Fracture mechanics, using the finite element method, is used to analyse the ply-drops. The influence of material and geometric parameters on the fracture energy release rate is investigated.