English: NIH expects that sex as a biological variable will be factored into research designs, analyses, and reporting in vertebrate animal and human studies. Strong justification from the scientific literature, preliminary data, or other relevant considerations must be provided for applications proposing to study only one sex. Investigators are strongly encouraged to discuss these issues with NIH program staff prior to submission of applications. In June 2020, the Journal of Women’s Health published “Sex as a Biological Variable: A 5-Year Progress Report and Call to Action,” an article commenting on the development and implementation of NIH’s SABV policy, which went into effect in January 2016. Further information regarding NIH expectations for the consideration of sex as a biological variable is provided in this guidance document.