The Second Edition (Revised) of the Industrial Source Complex Dispersion (ISC) Model User's Guide provides a detailed technical discussion of the updated ISC Model. The ISC Model was designed in response to the need for a comprehensive set of dispersion model computer programs that could be used to evaluate the air quality impact of emissions from large industrial source complexes. Air quality impact analyses for industrial source complexes often require consideration of factors such as fugitive emissions, aerodynamic building wake effects, time-dependent exponential decay of pollutants, gravitational settling, and dry deposition. The ISC Model consists of two computer programs that are designed to consider these and other factors so as to meet the dispersion modeling needs of air pollution control agencies and others responsible for performing dispersion modeling analyses. Major features in the revised model code include: (1) a regulatory default option: (2) a calms processing procedure; (3) a new Urban Mode 3; and, (4) revised sets of wind speed profile exponents for rural and urban scenarios.