Ultrasonographic (US) findings were correlated with clinical outcome in seven cases of meconium peritonitis detected with prenatal US during a 2-year period. Nineteen previously reported cases were also reviewed. US findings included intraabdominal calcifications (n = six cases), fetal ascites (n = 3), echogenic ascites without calcifications (n = 1), bowel dilatation (n = 2), and polyhydramnios (n = 5). Following delivery, six infants were still alive after a mean follow-up of 13 months (range, 6-26 months); the seventh died of hydrocephalus. Of the six, four required surgical correction of a small-bowel perforation and two did not. All six are thriving, and none has yet been found to have cystic fibrosis. In the 19 previously reported cases, there were only two cases of cystic fibrosis, neither with intraabdominal calcifications. The presence of calcifications was significantly associated with causes other than cystic fibrosis. Prenatally diagnosed cases of meconium peritonitis are associated with cystic fibrosis less frequently than previous studies suggest.