Gastrointestinal and abdominal manifestations of agnogenic myeloid metaplasia (AMM) were reviewed from the records of 122 patients with this disorder. Twenty-five percent of patients had abdominal pain of splenic origin. Hepatomegaly was present in 92 patients but excretory function of the liver generally remained good. Liver biopsies, carried out on 13 patients, showed AMM in all. The degree of hepatomegaly was paradoxically great in comparison to the relatively mild pathologic changes observed in liver biopsies. Nine patients had portal hypertension with esophageal varices and one of these also had ascites. Liver biopsies from three patients with symptomatic portal hypertension without obstruction of the extra-hepatic portal system showed only mild or moderate AMM. Our findings support the concept that increased portal blood flow is important in the pathogenesis of portal hypertension in patients wih AMM.