A 3-day-old thoroughbred filly, presented to Cornell's Equine Farm Animal Emergency Service for a one day history of diarrhea. On arrival, the filly was depressed, trembling, and had difficulty standing. Her vital parameters were within normal limits, but she had diarrhea staining on her hind limbs and passed pipe-stream diarrhea in the stall. She demonstrated several unsuccessful attempts to nurse in the stall. Blood work revealed electrolyte abnormalities, a metabolic acidosis, and a moderate hypoproteinemia. Initial stabilization included administration of intravenous fluids, dextrose, and oral electrolytes. Her diarrhea was treated with a broad spectrum regimen of antibiotics and gastroprotectants. The filly was placed on parenteral nutrition (PN) due to intolerance to enteral feeding, poor body condition, and weakness. She was given PN for 3 days. While no positive cultures were reported from the foal, we suspect the filly suffered diarrhea and sepsis due to Salmonella typhimurium shed from the mare. Her condition improved, but she was later diagnosed with septic thrombophlebitis and successfully treated with oral chloramphenicol.