Endoscopic ultrasound imaging of the gastrointestinal wall can be performed through intraluminal fluid or by direct transducer contact with the wall. We tested the hypothesis that the ultrasound appearance of the gastrointestinal wall is influenced by the amount of pressure applied when the transducer is in contact with the tissue. Fresh autopsy specimens from the porcine gastrointestinal tract were examined in vitro using an 8.5-MHz linear array ultrasound system. As transducer pressure against the wall was increased from 0 to 10 KPa, changes were seen on the images in wall thickness, tissue echogenicity, and the number of layers. The stomach and rectum were more resistant to compression than the esophagus, duodenum, and colon. Wall echogenicity increased with increasing degrees of applied pressure and some layers were obliterated by this pressure. The second ultrasound layer, or deep mucosa, appeared to be the most susceptible to compression. Endoscopic ultrasound imaging artifacts should be reduced by limiting the amount of pressure applied to the wall with the transducer.