Book excerpt: This issue of Veterinary Clinics of North America: Equine Practice focuses on Equine Gastroenterology, and includes topics: Diagnostics and treatment of undifferentiated and infectious acute diarrhea in the adult horse; Foal diarrhea; established and postulated causes, prevention, diagnostics and treatments; Probiotic use in equine gastrointestinal disease; Understanding the intestinal microbiome in health and disease; Advances in diagnostics and treatments in horses with acute colic and postoperative ileus; Advances in diagnostics and treatments in horses and foals with gastric and or duodenal ulcers; Toxic causes of intestinal disease in horses; New perspectives in equine intestinal parasitic disease Diagnostics and Management new insight; Equine disautonomia; Diagnostics and treatments in chronic diarrhea and weight loss in horses; Enteral/parenteral nutrition in foals and adult horses practical guidelines for the practitioner; and Practical fluid therapy and treatment modalities for field conditions for horses and foals with gastro-intestinal problems.