Millennials are increasingly reported to behave, and travel, differently from previous generations at the same stage in life. Among the observed changes, they postpone the time they obtain a driver’s license, often live in urban locations and do not own a car, drive less if they own one, and use alternative travel modes more often. However, the reasons behind these trends, and their long-term impacts on travel demand and the future growth of cities, are still largely unclear. This study investigates millennials’ mobility through the analysis of a comprehensive dataset collected among 2,155 young adults and members of the preceding Generation X who live in California, as part of a panel study of millennials’ residential choices, lifestyles, travel behavior and adoption of new technologies. The researchers present an overview of the research, and discuss results from the analysis of the California Millennials Dataset, focusing in particular on differences among millennials and Gen Xers in their attitudinal profiles, adoption of travel multimodality, vehicle miles traveled, and car ownership. The study provides useful insights for planners and policy-makers, through improving the understanding of millennials’ choices and the impact of lifecycle, period and generational effects on future travel.