Background: Ultrasound is widely accepted as a valuable diagnostic tool for detecting intra-abdominal and intrathoracic bleeding in trauma patients. Nevertheless, many doctors are reluctant to use it because they do not have sufficient training. This study aimed to define intraabdominal and intrathoracic fluid volumes that can be detected by sonography and their relation to fluid width in pigs to establish a clinically relevant animal model for teaching and training. Methods: Different volumes of normal saline were infused into the abdomen (50-2,000 mL) and chest (25-250 mL) in five anesthetized pigs. The maximum width of fluid as detected by ultrasound was recorded. The right upper quadrant, left upper quadrant, pelvis, and right paracolic section of the abdomen and right pleural cavity were studied. An experienced radiologist performed the studies. The effects on respiratory and cardiovascular functions were evaluated. Results: The sonographic findings in the pig were similar to those in humans. Up to 50 mL of intra-abdominal fluid and up to 25 mL of intrathoracic fluid could be detected by ultrasound. There was a significant correlation between the volume infused and the fluid width detected. The respiratory and cardiovascular monitoring of the animals showed that the infused intrathoracic volumes mimicked a survivable hemothorax. Conclusion: The pig may serve as an excellent clinically relevant model with which to teach surgeons detection of different volumes of intra-abdominal and intrathoracic fluids. The value of this model as an educational tool has yet to be tested.