It is disclosed herein that Brachyury is expressed in human tumors, specifically in tumors of the small intestine, stomach, kidney, bladder, uterus, ovary, and testes, as well as in lung, colon and prostate carcinomas. Immunogenic Brachyury polypeptides are disclosed herein. These polypeptides can be used in diagnostic assays for Brachyury expression, as well as for inducing an immune response to Brachyury. Polynucleotides encoding the immunogenic Brachyury polypeptides, vectors including these polypeptides, host cells transformed with these vectors, and methods of using these polypeptides, polynucleotides, vectors, and host cells are provided. Methods of diagnosing a Brachyury-expressing cancer are also provided. Exemplary cancers include small lung, colon, intestine, stomach, kidney, bladder, uterus, ovary, and testes and prostate cancers. Methods of treating cancer are also disclosed.