Over the past 20 years, the Transport and Road Research Laboratory has carried out a co-ordinated programme of fatigue testing, including work on the fatigue performance of reinforced and pre-stressed concrete beams. The research has led to a better understanding of the fatigue behaviour of plain concrete, the various types of reinforcing bars in air and concrete, continuous welded, lapped and coupled bars, and the effects of corrosion. The work of TRRL and many other organizations is reviewed and a summary of current design rules with recommendations for assessing the fatigue life of new structures in service is given.