A detailed presentation of the major role played by correctly designed and fabricated joints in the safe and reliable response of steel, composite and timber structures. The typology/morphology of connections is discussed for both conventional pinned and rigid joints and semi-rigid types. All relevant topics are comprehensively surveyed: definitions, classification, and influence of joint behaviour on overall structural response. Also presented are the application of the component method, the notion of rotational capacity, the local ductility of different types of earthquake-resistant structural joints as determined in cyclic experiments, numerical techniques for the realistic simulation of joint response, simple and moment-resistant structural connections.