Electromagnetic interference (EMI) shielding of windows and domes in electro-optical (EO) systems can be accomplished by transparent electrically conductive (EC) coatings or patterned opaque EC coatings. The shielding effectiveness (SE) of these two methods was studied both analytically and experimentally. Shielding due to both absorption and reflection as a function of frequency was evaluated. Infrared EO systems often use windows or domes made of semiconductive material. These semiconductive materials also provide some EMI shielding for the system. The SE of some typical exemplary semiconductive windows was calculated. The broadband shielding benefits of using EC coatings deposited on semiconductive window substrates were examined.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.