The story of the investigation of the MIC toxic gas tragedy in Bhopal (more than 3,700 deaths)and the LPG disaster in Mexico City (500 fatalities), the difficult circumstances of the investigations and the results. Have we learned any lessons? Unique information like the original technical drawings of the Bhopal plant. Information about LPG safety, also by describing other LPG disasters. Various explosions (BLEVE's) of LPG road tankers are discussed. The underlying causes of the failure of safety management. Developments in 25 years are analysed. The disasters of 1984, compared with more recent incidents, such as an explosion in a furnace (Geleen, 2003), and the refinery disaster in Texas (USA) in 2005. Land use planning policies failed dramatically in Mexico and Bhopal. The existing (QRA) policy in Europe for "safe distances" around plants with hazardous substances will prevent that large number of victims are likely. However, the underlying causes of Mexico City and Bhopal are still present. Process Safety Annexes: Contemporary methods for process safety as HAZOP, LOPA, SIL and incident investigation (Tripod) are described and elaborated through examples.