In developed countries, the years from Age 30 to 45 are, for many, the most intense, demanding, and rewarding years of adult life. During this period of the life span most adults must negotiate the intersecting demands of progressing in a chosen career, maintaining an intimate partnership, and caring for children. Successes or difficulties in meeting these simultaneous demands have the potential to profoundly influence the direction of a person's adult life. As such, we believe that it is of critical importance to better understand this developmental period that we call established adulthood. This article provides a new theoretical conceptualization of established adulthood, outlining its distinctiveness from emerging adulthood and midlife in terms of physical health, well-being, cognitive development, and the career-and-care-crunch of competing work and family responsibilities. We also consider variations in the timing and experience of established adulthood, including variations by gender and social class, and provide suggestions for future research. As economic and social arrangements continue to evolve, so too will this developmental period, providing fertile ground for developmental theory and research. (PsycInfo Database Record (c) 2020 APA, all rights reserved).