Ultrasound scanning using a 13 MHz probe was performed on 158 infants, aged 12 weeks or less, presenting with conjugated hyperbilirubinaemia. The gall bladder was identified in 156 infants, 35 of whom had biliary atresia. The two patients in whom no gall bladder was seen both had biliary atresia. The gall bladder shape was normal in 128 patients (9 with biliary atresia) and irregular in 28 patients (26 with biliary atresia). The gall bladder wall was regular in 121 patients (4 with biliary atresia) and irregular in 35 patients (31 with biliary atresia). Combining these findings gave a sensitivity of 91.9%, a specificity of 96.7%, a positive predictive value of 89.5%, a negative predictive value of 97.5% and an accuracy rate of 95.6% for ultrasound of the gall bladder in the identification of biliary atresia. This compares with 90%, 92.4%, 75.3%, 97.3% and 91.9%, respectively, in our previous report using a 7 MHz probe.