In Erikson's model of development, intimacy and isolation denote polar outcomes of psychosocial crisis in young adulthood. Drawing on this model, the present study used three-wave longitudinal data to examine patterns of the success and lack of success in the resolution of Eriksonian crisis in relation to romantic loneliness as a negative outcome of the intimacy crisis, and compared across Poland and the United States. The data were collected from Polish and U.S. individuals aged 18-40 for Wave 1 (N = 763). Four patterns of the Eriksonian intimacy crisis were identified: (a) stable partnered status; (b) stable single status; (c) transition from single to partnered status; (d) transition from partnered to single status. In both countries, transition from single to partnered status was related to decreased romantic loneliness. Greater initial romantic loneliness was observed among Polish single adults who transited to partnered status in contrast to stable single adults. In turn, the U.S. partnered adults who transited to single status initially experienced lower romantic loneliness than stable single adults. Bivariate latent growth curve models pairing romantic loneliness with relationship satisfaction revealed that higher initial relationship satisfaction was associated with lower initial romantic loneliness, and a greater increase in relationship satisfaction was associated with smaller increases in romantic loneliness. The findings highlight that different resolutions of the intimacy crisis are related to diverse romantic loneliness and relationship satisfaction trajectories and these associations also appear to differ as a function of various marital and loneliness contexts in Poland and the United States. (PsycInfo Database Record (c) 2022 APA, all rights reserved).