Cross-national comparisons of data from developed countries offer useful insights into the retirement process and policy. Here we summarize findings for older persons age 50-70 using new microdata files collected by the Japanese Study of Aging and Retirement (JSTAR) project, and we compare these with results in the U.S. Health and Retirement Study (HRS). We examine the relative importance of health, wealth, family, and other factors in work and retirement at older ages cross-nationally. Though both countries have relatively high employment at older ages, the Japanese have longer life expectancy, higher levels of financial wealth, and a lower public pension eligibility age. Our analysis, the first to compare these two rich data sources, suggests two conclusions (subject to revision when data weights become available). First, older Americans differ in key ways from their Japanese counterparts, particularly along educational, health, and wealth dimensions. Second, in some cases, there is a distinctly different impact of these factors on labor force outcomes. Specifically, age, sex, education, and wealth influence behavior differently across the two countries, though being obese or having better mental acuity/financial literacy scores has no differential impact. Thus observed differences in work patterns between Americans and Japanese at older ages are attributable to some identifiable factors; moreover, the results can be used to project future responses to changes in education, age, health, and wealth in order to account for the large differences in older workers’ work patterns at older ages in Japan and the US.