The case of a 22-year-old patient with a thoracoabdominal duplication of the alimentary tract is described. The chest radiograph, with a large cyst in the posterior mediastinum and vertebral abnormalities and a barium swallow showing the abdominal part of the duplication, were diagnostic. At operation a malrotation of the midgut was found and the duplication was resected, leaving esophagus and small bowel intact. An explanation for association of the two malformations - vertebral abnormalities and malrotation - was sought in the literature, particularly that concerning embryogenesis. The following conclusions were reached: 1. Duplications of the alimentary tract are a heterogeneous group with three different embryological faults in development. 2. According to the so-called notochordal theory, vertebral abnormalities and malrotation of the midgut are usual and should be expected in thoracoabdominal duplications of the alimentary tract.