The LCLS Diagnostics and Commissioning Workshop was held at the University of California at Los Angeles (UCLA) on January 19-20, 2004 to establish the basis for a plan (published under separate cover) to commission the Linac Coherent Light Source (LCLS) undulator line with the final goal of saturating the FEL process down to the shortest fundamental x-ray wavelength of 1.5 Angstrom. The workshop focused on requirements for the generation and characterization of x-ray radiation during the commissioning phase including electron beam control, electron and x-ray beam diagnostics, as well as the development of simulation codes to support commissioning. The workshop was presented with a proposal for commissioning diagnostics and with procedures to carry out FEL commissioning towards the end of the LCLS construction phase.