One hundred seventy-nine subjects took part in a test-retest study to investigate the formation of flashbulb memories (FMs) related to two notable events in 1995: the Nerve Gas Assassins’ Attack and the Gubernatorial Election in the Tokyo Metropolitan District. A causal analysis using the structural Equations (EQS) technique showed that the formation of FMs related to the former was primarily associated with the level of IMPORTANCE AND ESTIMATION of the event, while that of FMs related to the latter was primarily associations with AFFECT. These results suggest that the mechanisms of FMs formation do not converge into one mechanism. The implication of these findings is that studies of the formation of FMs need to take account of the characteristics of the events triggering them.