Radiation technology is one of the most important fields which the IAEA supports and promotes, and has several programmes that facilitate its use in the developing Member States. In view of this mandate, this Booklet on “Gamma Irradiators for Radiation Processing” is prepared which describes variety of gamma irradiators that can be used for radiation processing applications. It is intended to present description of general principles of design and operation of the gamma irradiators available currently for industrial use. It aims at providing information to industrial end users to familiarise them with the technology, with the hope that the information contained here would assist them in selecting the most optimum irradiator for their needs. Correct selection affects not only the ease of operation but also yields higher efficiency, and thus improved economy. The Booklet is also intended for promoting radiation processing in general to governments and general public. The Booklet is prepared by the IAEA’s Industrial Applications and Chemistry Section, Division of Physical and Chemical Sciences with the assistance provided by consultant Mr. Kishor Mehta. The IAEA staff member responsible for this project was Mr. Andrzej G. Chmielewski. The IAEA is grateful to all persons and organizations that provided valuable information for the Booklet.