Underlying Events and Diffraction Studies at the LHC

The potential of the LHC experiments to study the underlying events and diffractive in proton-proton collisions at sqrt{s} =14 TeV is described. The underlying event is studied by examining charged particles in the region transverse to jets and in the central region of Drell-Yan muon-pair production. The diffractive program includes studies of QCD, low-x structure of the proton, and central exclusive production of SM and MSSM Higgs. The measurement of the scattered protons at appropriate locations along the beam-line is especially useful at high instantaneous luminosities.