An improved hot-side electrostatic precipitator is provided which more efficiently removes particulates such as fly ash from gases by substantially decreasing the occurrence of back corona discharge. The improved hot-side electrostatic precipitator is based upon the discovery that back corona discharge occurs primarily, if not entirely, in the accumulated particle layer in those sections of the collection plates having a temperature low enough to initiate back corona discharge.Based on this recognition, the corona electrodes and collection plates of the present invention define an upper laterally extending primary operating region having a temperature substantially throughout that is greater than a first value and having at least a portion with a localized electric field strength in the primary operating region greater than a second value, and a lower laterally extending secondary operating region having a temperature substantially throughout that is less than the first value and a localized electric field strength substantially throughout that is less than the second value. The first and second values are selected so that the likelihood of back corona discharge is reduced.