Objective: The study documents whether socioeconomic status (SES) differentials in biological risk are more widely observed and larger in the United States than Taiwan. Method: Data come from the Social Environment and Biomarkers of Aging Study in Taiwan and the Midlife in the United States study. We use regression analyses to test whether four summary measures of biological risk are significantly related to categorical measures of education, income, and subjective social status among four country–sex-specific subgroups. Results: Physiological dysregulation is significantly, negatively related to SES in both the United States and Taiwan, especially for males. The prevalence and magnitude of the relationships are similar in the two countries: 12 of 24 possible SES–biological summary score relationships are significant in the United States and 11 of 24 are significant in Taiwan. Discussion: Overall, SES differentials in biological risk do not appear to be more widely observed or larger in the United States than in Taiwan.