The proceedings of DIS 2001 present the most updated status of deep inelastic scattering (DIS) physics. Topics like structure function measurements and phenomenology, QCD studies in DIS and photoproduction, spin physics and diffractive interactions are reviewed in detail, with emphasis on those studies that push the test of QCD and the Standard Model to the limits of their present range of validity, towards both the very high and the very low four-momentum transfers in the lepton-proton scattering. Moreover, this workshop coincided with the transition between the first period of...