A quantitative study of white pulp arterial vessels has been carried out in congestive splenomegaly with hypersplenism. Arteries and arterioles with periarterial lymphatic sheath (PALS) in abnormal spleens show an absolute volume and total length higher than in controls. Moreover, they present a luminal diameter significantly lower than normal. These findings demonstrate an increase of the white pulp arterial bed in congestive splenomegaly. Thus, the arteries with PALS participate in the complex vascular rearrangement which supports the blood hyperflow in congestive splenomegaly.