Tropical splenomegaly is a pathologic condition due to multiple causes, endemic malaria being the major one. Twenty-eight black patients, 10 males and 18 females, residing in a tropical area, were investigated with US. The morphological features and major diameters of the spleen were studied and the splenic volumetric index (IVS) was calculated. Typical features were the presence of small intraparenchymal calcifications (46%) and the enlargement of splenic vessels, with US wall reinforcement (75%). No nodular lesions were detected, but increased frequency of organ lobulation was observed. A definite and uniform increase in splenic diameters was seen in all cases; IVS in particular was greater than the accepted confidence limit (21.5 +/- 6.5). This characteristic features should help the echographist to recognize this condition for they supply useful clinical information.