Anorectal atresia results from abnormal development of the anorectal septum. Prenatal diagnosis is difficult but the condition may be suspected by the sonographic demonstration of a dilated colon. We present the sonographic features of a fetus with anal atresia and a ventricular septal defect at 12 weeks of gestation. This case illustrates that a dilated colon may be present in association with fetal anal atresia as early as 12 weeks.