Toca 511 is a novel retroviral replicating vector, encoding a modified yeast cytosine deaminase, administered to recurrent high grade glioma patients in Phase 1 trials by stereotactic, transcranial injection into the tumor or into the walls of the resection cavity. A key issue, with little published data, is vector biocompatibility with agents likely to be encountered in a neurosurgical setting. We tested biocompatibility of Toca 511 with: delivery devices; MRI contrast agents, including ProHance supporting coinjection for real time MRI-guided intratumoral delivery; hemostatic agents; biofluids (blood and cerebrospinal fluid); potential adjuvants; and a needleless vial adapter that reduces risk of accidental needle sticks. Toca 511 is stable upon thawing at ambient temperature for at least 6 hours, allowing sufficient time for administration, and its viability is not reduced in the presence of: stainless steel and silica-based delivery devices; the potential MRI contrast agent, Feraheme; ProHance at several concentrations; the hemostatic agent SURGIFOAM; blood; cerebrospinal fluid; and the needleless vial adapter. Toca 511 is not compatible with the hemostatic agent SURGICEL or with extended exposures to titanium-based biopsy needles.