Although process hazard analyses have been voluntarily used 117 the chemical processing industries for over 30 year, and required by US regulation for certain processes involving highly hazardous chemicals since the early 1990s. failing to apply or continued misapplication of these techniques allow process hazards to remain either undetected or unappreciated Using findings from past CSB investigations as examples, this article discusses some problems observed in process hazard analyses that diminished their overall effectiveness and prevented them filly identifying and/or evaluating process hazards Some practical solutions are presented for making process hazard analyses more effective Published (C) 2010 American Institute of Chemical Engineers Process Sal Prog 29 264-269, 2010