Selected topics in the field of pile foundations are addressed. The effects of the installation technique on the bearing capacity and the load-settlement response of a single pile are discussed. The latter effect is shown to be less significant; a settlement controlled design is thus less dependent on the technological factors. Monitoring of the installation parameters shows some potential for controlling the pile response. The available experimental evidence on the behaviour of pile foundations under vertical loads (settlement, load sharing, bearing capacity), by monitoring of full scale structures or by research experiments, is reviewed. Simple empirical methods for a preliminary evaluation of the settlement are suggested. The (more limited) evidence about horizontal loading is also reviewed and discussed. The methods for the analysis of pile foundations under vertical load are next reported. They may be considered satisfactory for engineering purposes, provided they are used paying due attention to the correspondence relations between theories and reality. The criteria for an optimum design, achieving maximum economy while keeping satisfactory performances, are different for different kinds of pile foundations (small groups, large rafts). Safety against a bearing capacity failure, average settlement, differential settlement, moment and shear in the raft and cost are the quantities to be controlled. It is claimed that the conventional capacity based approach, still prevailing in practice, is not suited to develop a proper design. Present codes and regulations, essentially based on this approach, at the time being act as a restraint rather than a stimulus and need some revision.