In this study, an inventory of the hydrophobicity of peritoneal tissues in the living rat was made. Peritoneal tissues were divided into mesentery (i.e., omentum) and parietal and visceral peritoneum and their hydrophobicity was determined by the sessile drop method. All peritoneal tissues were hydrophilic with water contact angles varying from 0degrees to 61degrees. Mesentery and visceral peritoneum covering the intestines were significantly more hydrophilic than parietal and other visceral peritoneal tissues. In general, visceral peritoneum was the most hydrophobic tissue, and visceral peritoneum covering the kidneys (61degrees) and the stomach (54degrees) was less hydrophilic than that covering the rest of the organs, i.e., spleen (49degrees), liver (45degrees), and bladder (41degrees). In summary, peritoneal tissues involved in adsorptive and exchange functions and requiring lubrication are more hydrophilic than tissues with more important and protective functions.