Calcified portal vein thromboemboli are not, as a rule, considered in the differential diagnosis of abdominal calcifications in the hepatic area in infants. A review of 13 autopsy cases with a retrospective examination of available chest and abdominal films showed that this entity could have been recognized in some instances (1). More recently, the roent-genographic diagnosis of calcified portal vein thrombi antemortem was suggested in 2 patients and verified at autopsy. This article presents the main clinical and radiological data from a series of 21 cases, 19 collected since 1954, representing 0.6 per cent of all perinatal and pediatric autopsies in this period. More detailed clinicopathological correlations, pathologic observations, and pathogenetic mechanisms will appear in a subsequent paper. Gross and Microscopic Anatomy The lesions may be single or multiple. They are usually subcapsular, appearing as nodules or as zig-zag or branching lines of a chalky-yellow color, and average less than 1 mm in width and 2 mm to 1 or 2 cm in length. They frequently run parallel to the liver capsule at the bottom of shallow depressions. Deeper thrombi commonly accompany the more superficial ones, and the affected area may show extensive fibrosis secondary to focal infarction (Figs. 1 and 2). All thrombi obliterated completely the involved portal veins, sometimes with evidence of recanalization. Most were organized and calcified en masse or as more or less confluent tiny psammous bodies; a few recent thrombi could be found at the periphery of older lesions, and some purely fibrous obstructions without calcification were identified (Figs. 3 and 4). The pattern of a linear or branching structure was fairly consistent and reflected in the roentgen appearance of peripheral calcifications. In some very extensive lesions, usually associated with infarction, thrombi reached from one large branch toward the periphery in a distinctive “cauliflower” pattern, also identifiable on films. Location and Distribution (Table I) The majority of the lesions were found in the left lobe of the liver. Only two single ones and one group of thrombi were located in the right lobe. The left lobe, usually at its most peripheral zone, twice showed multiple and six times single phleboliths. The calcifications were multiple and distributed in both lobes in nine cases. In addition, one “staghorn” phleb-olith was identified in the ductus venosus extending into the portal sinus. Roentgenographic Appearance and Differential Diagnosis As the patients generally died soon after birth, the only clinical studies were chest films. In sick premature infants, however, portable films are the rule, and the upper abdomen is well included, allowing visualization of the hepatic area in frontal and lateral views.