Sex and gender are important variables in research, but they are inconsistently explored. The international PAINDIFF Network makes 13 recommendations for studying sex and gender as variables in pain research, which are applicable across the spectrum of biopsychosocial research. Five universal recommendations apply to the majority of research studies:(1) include males and females as standard practice, (2) account for sex in randomization or counterbalancing and testing order, (3) power for sex differences when sex is a primary experimental variable, (4) include detailed reporting of experimental design, and (5) conduct sex disaggregated analysis and reporting. Three additional recommendations specifically for preclinical studies and five additional recommendations for human and clinical studies are included. Recommendations for stakeholders, such as editors, reviewers, funding bodies and policymakers, have also been developed. Wide adoption and implementation of these recommendations will reduce variability, improve reproducibility and enhance the translatability of research findings within and beyond the field of pain.