The effect of right paralumbar fossa exploratory celiotomy and omentopexy on peritoneal fluid constituents was studied in 22 adult dairy cows. Six cows were eliminated on the basis of physical examination findings (n = 2), surgical findings (n = 2), or inability to obtain a sufficient volume of peritoneal fluid (n = 2). Sixteen cattle had normal results of CBC and serum biochemical analysis, and a minimum of 1 ml of peritoneal fluid was obtained by abdominocentesis. Abdominocentesis was repeated on days 1, 2, and 6 after surgery. Statistical analysis for repeated measures was performed, using a significance level of P < 0.05. Stage of gestation was evaluated for interaction with time. Mean total nucleated cell count was 3,200 cells/microliters before surgery, was significantly increased 2 days after surgery (16,336 cells/microliters), and continued to increase through day 6 (20,542 cells/microliters). Mean polymorphonuclear cell count was 1,312 cells/microliters before surgery and was significantly higher at 2 (11,043 cells/microliters) and 6 (10,619 cells/microliters) days after surgery. Mean lymphocyte count was 254 cells/microliters before surgery and was significantly increased 2 days (1,911 cells/microliters) after surgery. By day 6, lymphocyte numbers were similar to preoperative values. Mean mononuclear cell count was 770 cells/microliters before surgery and was significantly increased on days 1 (3,084 cells/microliters), 2 (3,285 cells/microliters), and 6 (2,349 cells/microliters) after surgery. Mean eosinophil numbers were 1,388 cells/microliters before surgery and were significantly increased on day 6 (6,347 cells/microliters) only. Interaction between time and stage of gestation was found only for specific gravity and total protein concentration.(ABSTRACT TRUNCATED AT 250 WORDS)