Many pufferfish possess tetrodotoxin (TTX). Unaware of this fact, the owner of a 3-mo-old pet Cuvier's dwarf caiman (Paleosuchus palpebrosus) fed the caiman a green spotted pufferfish (Tetraodon nigroviridis), acquired from a local discount department store. The caiman was nonresponsive within an hour of consumption of the fish. The caiman was presented for veterinary evaluation but died despite intensive medical care. High-performance liquid chromatography and a competitive inhibition enzyme immunoassay were used to determine whether the pufferfish was tetrodotoxic and whether the deceased caiman had TTX in its system. Skin and liver of the pufferfish harbored high concentrations of TTX, and the caiman had TTX in the blood, liver, and kidney. The clinical signs and presence of TTX in the caiman suggest that the caiman succumbed to tetrodotoxicosis. The implication is that lethally poisonous species are available commercially and pose a danger to other pets and possibly small children.