Abstract. Lead (Pb) poisoning of a pregnant heifer was diagnosed based upon clinical signs (head pressing, blindness, muscle twitching) and a blood lead concentration of 1.73 ppm. Blood and urinary Pb half-lives with CaNa 2 EDTA/thiamine therapy were determined to be 2.08 and 1.38 days, respectively. Many cations (Ca, Fe, Zn, Na, Cu), including Pb, were excreted at higher concentrations in urine during therapy. Blood (0.425 ppm) and liver (4.85 ppm) Pb concentrations in the fetus were 71.7% and 84.3% of the same tissue Pb concentrations of the dam, indicating a significant transfer of Pb in utero. Severe polioencephalomalacia was described in the adult, and hepatic lysosomes with metallic electron densities were present in the fetus.A severely depressed and dehydrated approximately 10-month-old angus heifer (175 kg, estimated) was presented to the Mississippi State University, College of Veterinary Medicine (CVM) Animal Health Center. The herd had recently experienced 2 acute yearling deaths due to unknown causes. This heifer had been found standing in a pond and was reluctant to move. Clinical signs included head pressing, staggering, muscle twitching, and lack of a menace response. Acute toxicosis (lead [Pb], organic pesticides, mercury) or a vitamin deficiency (vitamin A, thiamine) were suspected. Other rule outs included rabies, polioencephalomalacia, thromboembolic meningoencephalitis, listeriosis, and other less common central nervous system (CNS) differential diagnoses. 21 Blood was taken for a complete blood count (CBC) with differential, serum chemistry panel, and blood Pb concentration analysis. Initial therapy (day 0) consisted of thiamine hydrochloride a (1 g, intramuscular [im]), dexamethasone b (20 mg, intravenous [iv]), and oral electrolyte solution c (10 liters via stomach tube).The following morning the neurological signs were more pronounced and included, in addition to those previously noted, hyperesthesia, ptyalism, and bruxism. Blood Pb concentration was 1.73 ppm (CVM Diagnostic Services, Toxicology Laboratory, normal < 0.35 ppm) and the CBC and clinical chemistries were unremarkable. Day 1 treatments were 10 liters electrolyte solution per os, CaNa 2 EDTA d (13 g in 250 ml of saline iv), thiamine hydrochloride (1 g, im), and acepromazine maleate e (18 mg, im