We report the results of a prospective series of 60 consecutive splenectomies for hematologic disorders performed between February 1995 and May 1996. The portal venous flow of all the patients (34 men and 26 women with a mean age of 54.1 years) was systematically studied before and after intervention with Doppler color imaging (on the day before the intervention and on the 7th and 30th postoperative days). The objective of this study were to determine the real frequency of asymptomatic portal or splenic venous thrombosis (PSVT) after hematologic splenectomy. The intervention began with exteriorization of the spleen and the tail of the pancreas; ligation of the splenic vein was performed close to its junction with the inferior mesenteric vein. Twenty-three complications (38.3%) were noted with three deaths (5%). One symptomatic PSVT (1.6%) and three asymptomatic PSVTs (6.7%) were diagnosed and treated with no deaths. Three risk factors of PSVT, recognized by all the authors, were present in these four cases: large splenomegaly, thrombocytosis, or myeloproliferative disorder. The systematic ultrasonographic (US) examinations increased the frequency of diagnosis of PSVT sevenfold during the perioperative period. Patients with marked splenomegaly associated with lymphoma, chronic lymphocytic leukemia, or myeloid metaplasia probably require systematic US monitoring during follow-up, but this must be determined by further study.