Hypoxia, a consequence of tumor cells outgrowing their blood supply, and subsequent angiogenesis are two of the hallmarks of rapidly growing solid tumors. My group has been exploiting these unique pathological features for developing novel therapeutic approaches. One example is the development of C. novyi-NT, an attenuated strain of the anaerobic bacterium Clostridium novyi. The hypoxic tumor compartment poses challenges for both chemo and radiation therapies as hypoxia diminishes the therapeutic effects of chemotherapeutic agents and radiation. Conversely, this tumor compartment, hypoxic and immune-privileged, provides a unique niche for anaerobic bacteria to grow. We therefore generated C. novyi-NT, which has shown substantial therapeutic effects in experimental tumor models. A human Phase I trial and several canine trials are currently being conducted.