American poison control data were analyzed comparing 130 suicidal antifreeze ingestions occurring in 2 states after enactment of bittering requirements with 3,493 cases occurring in states (or at times) where bittering was not required. The frequency of suicidal antifreeze ingestions was unchanged after implementation of bittering. The volume implicated, medical outcome distribution, & use of antidotes, hemodialysis, intubation, or critical care, showed no significant difference between bittered & non-bittered groups. Bittering was not a significant contributor in predicting lethal or life-threatening medical outcomes. It is concluded that, using American poison control data, the addition of bittering agencts to antifreeze is not justified.