Abstract: The present invention provides genetic markers on human chromosome 6 that are associated with a beneficial response to a treatment that targets Clostridium difficile (C. difficile) toxin B (TcdB), e.g. a TcdB antibody. These TcdB treatment response markers are useful, inter alia, to identify patients who are most likely to benefit from treatment with a treatment that 5 targets TcdB in methods of treating patients having a disease susceptible to treatment with a TcdB antibody, and in methods for selecting the most appropriate therapy for such patients. The invention also provides antibodies, drug products, and kits useful with the TcdB Treatment response markers of the invention.