Abstract Lifestyle risk factors are important precursors of old age disease and disability, and the population level impact of these factors likely differs across countries that vary in their economic growth and the attributes of the populations that adopt and abandon unhealthy lifestyles. This paper describes the stage of â€œlifestyle transitionâ€ among older adults in two countries with vastly different trajectories of socio-economic development. A series of hypotheses are proposed on the socioeconomic patterns of health risk factors that would be expected in the two countries, given their economic circumstances and the historical timing of policy interventions that were initiated to mitigate lifestyle risks in these populations. The paper compares the prevalence of smoking tobacco, drinking alcohol, obesity, and lack of physical exercise, as well as the socioeconomic and demographic covariates of these risk factors, among adults aged 55 and older in Mexico and the United States. The findings indicate that smoking- and physical-activity-related transitions toward healthier lifestyles are well under way among older adults in the United States but not in Mexico, whereas a trend toward reduced levels of obesity has just begun in the United States but not in Mexico. There is no evidence of a transition in heavy alcohol drinking in either country among older adults.