A fatal overdose involving case by 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is reported. 5-MeO-DIPT and its two metabolites, 5-hydroxy-N,N-diisopropyltryptamine (5-OH-DIPT) and 5-methoxy-N-isopropyltryptamine (5-MeO-NIPT), were identified by LC-MS. The level of 5-MeO-DIPT, 5-OH-DIPT and 5-MeO-NIPT in blood and urine was 0.412, 0.327 and 0.020 microg/ml, and 1.67, 27.0 and 0.32 microg/ml, respectively. These blood and urine levels were higher than published data for such poisoning.