Forensic autopsies were performed on 1,821 cases in 2014 and 2,024 cases in 2015 at the National Forensic Service Seoul Institute. Based on the autopsy reports, 103 cases (5.7%) in 2014 and 130 cases (6.4%) in 2015 were selected as unnatural deaths caused by fatal intoxication. The cases were divided into five groups. The first group had ethanol intoxication, the second had drug intoxication, the third had agrochemical intoxication, the fourth had cyanide intoxication, and the fifth had miscellaneous intoxications. Of the 233 cases, 202 had death certificates. Of these 202 cases, 169 (83.7%) had an undetermined manner of death (MOD); 17 (8.4%) had an unnatrual MOD and intoxication was the cause of death (COD); nine (4.5%) had an unnatural MOD, but the COD was not intoxication; seven (3.5%) had a natural MOD and disease as a COD. The predictive ratios of intoxication as a COD were compared with the death certificates and the police death scene investigation results. The death certificates and the police investigation results showed predictive ratios of 8.4% and 55.2%, respectively, for intoxication as a COD. The discrepance in these predictive ratios and relatively low predictive ratio of police investigation results mean that intoxicated deaths have been underevaluated; thus, some homicides or intentional deaths were probably missed under South Korea's death investigation system. Doctors who specialize in forensic medicine need to supervise the entire postmortem examination process and emergency blood toxicological analysis should be performed in South Korea.