Third-generation rabies viral vectors have low toxicity and improved efficiency as retrograde labeling tools.

In this issue of Cell Reports Methods, Jin et al. report the generation and validation of a rabies variant, RVΔL, for projection-based neuronal labeling. RVΔL shows little toxicity in vivo and has an improved growth advantage over another variant, RVΔGL, making it a useful tool for a wide variety of systems neuroscience-based studies.