Racial health inequality is related to socioeconomic status (SES), but debate ensues on the nature of the relationship. Using the US National Health and Nutrition Examination Survey I and the subsequent follow-up interviews, this research examines health disparities between white and black adults and whether the SES/health gradient differs across the two groups in the USA. Two competing mechanisms for the conditional or interactive relationship between race and SES on health are examined during a 20-year period for black and white Americans. Results show that black adults began the study with more serious illnesses and poorer self-rated health than white adults and that the disparity continued over the 20 years. Significant interactions were found between race and education as well as race and employment status on health outcomes. The interaction effect of race and education showed that the racial disparity in self-rated health was largest at the higher levels of SES, providing some evidence for the "diminishing returns" hypothesis; as education levels increased, black adults did not have the same improvement in self-rated health as white adults. Overall, the findings provide evidence for the continuing significance of both race and SES in determining health status over time.