Using daily diary data from 81 same-sex couples, we examined the link between stress experienced outside the relationship (external) and within the relationship (internal) for individuals (stress spillover) and their partners (stress crossover). Extending prior literature, we examined spillover and crossover of both common external (e.g., work stress) and sexual minority stress (e.g., discrimination based on sexual orientation) and the extent to which individuals' own and their partner's difficulties in emotion regulation moderated these associations. We found compelling evidence for spillover of common external stress and crossover of both types of stress. Further, we found both concurrent (same day) and lagged (next-day) stress spillover and crossover processes for both types of external stressors, moderated by both partners' reported difficulties in emotion regulation. Findings related to stress spillover and crossover as well as implications for researchers and clinicians working with same-sex couples are discussed. [ABSTRACT FROM AUTHOR]