Tribromoethanol is a popular injectable anesthetic agent commonly used for embryo-transfer surgery for the generation of transgenic mice and sometimes rats. In humans and animals, Tribromoethanol produces a generalized CNS depression, including both the respiratory and cardiovascular centers. It undergoes conjugation with glucuronic acid during metabolism in the liver, followed by excretion in the urine as TBE glucuronate. Tribromoethanol causes rapid and deep anesthesia followed by rapid and full postoperative recovery, but the margin of safety between anesthetic and the lethal dose is narrow. Depression of respiration and circulation, together with its general unpredictability, eventually discouraged its use. Although Tribromoethanol solutions are often referred to as Avertin, this is a misnomer. Avertin was the trade name for Winthrop Laboratories’ proprietary Tribromoethanol formulation, which is no longer available. Marketing of pharmaceutical-grade Tribromoethanol took place under several proprietary names, including Avertin, Bromethol, Ethobrom, and Narkolan, each as a 66.7% (w/w) solution of Tribromoethanol in tertiary-amyl alcohol, wherein each milliliter contained 1 g of Tribromoethanol. Although pharmaceutical-grade TBE has not been commercially available or routinely used for human or veterinary anesthesia for several years, the agent has received widespread acceptance for use in the various manipulations required for the production of genetically engineered mice and rats. Tribromoethanol is an attractive anesthetic choice for many researchers because it is easy and inexpensive to make in the laboratory from readily available reagents, requires no special equipment for its administration, and is not subject to federal or state drug enforcement agency storage or accountability regulations. More importantly, the i.p. injection of TBE results in the simple and rapid induction of short-term surgical anesthesia sufficient for the vasectomy, embryo transfer, and tail amputation for Southern blot analysis—all necessary elements in the production of genetically engineered animals.