The paper discusses an experimental research program to characterize back-corona generation and behavior in a range of environments and geometries common to electrostatic precipitators (ESPs). A wire-parallel plate device was used to monitor the intensity and distribution of back-corona discharges. Back-corona was generated by subjecting a deposited layer of fly ash to corona current. Back-corona emissions were observed with a sensitive video camera. These observations provided new insight into the characteristics of back-corona phenomena. Conditions that were varied during the experiments included ash resistivity, corona electrode design, corona polarity, and ash-layer thickness and surface condition. The effect of pulsed energization on back-corona was also studied. Analyses of visual observations and measured distributions of corona and back-corona current allowed an assessment of the effects of back-corona emissions on ESP operating parameters. (Copyright (c) 1987 Elsevier Science Publishers B.V.)