2,4-Dinitrophenol (2,4-DNP), a yellowish compound, has historically been used in the manufacture of dyes, explosives, and fungicides. As it uncouples mitochondrial oxidative phosphorylation, the compound was also used as an antiobesity agent early in the past century. The compound was subsequently banned by the United States Food and Drug Administration in 1938 due to its potentially fatal adverse effects, including hyperthermia, cataract, agranulocytosis, hepatoxicity, nephrotoxicity, and cardiotoxicity. However, the popularity of 2,4-DNP as a slimming aid has appeared to increase again in recent years. The Hong Kong Hospital Authority Toxicology Reference Laboratory recently confirmed two cases of self-administered 2,4-DNP with different clinical presentations to hospitals in the area. Here we describe those two cases, in an attempt to underscore the potential of misuse of this substance by body-conscious groups among the Chinese population.