Six cases of mesenteric venous thrombosis have occurred in the metropolitan area from 1982 through 1985. The most common findings were nonspecific abdominal pain associated with nausea and vomiting, subjective distress disproportionate to the objective findings, and signs of decreased intravascular fluid volume. In all six cases there was a rapid progression of physical findings to a level commensurate with the initial complaint. The most consistent laboratory abnormalities were an increase in leukocyte precursors, an elevated lactate dehydrogenase, and a mild metabolic acidosis. Mesenteric venous thrombosis is an unusual disease that is difficult to diagnose and manage.