A robust and very persistent association between indicators of socioeconomic status (SES) and the onset of life-threatening disease is a prominent concern of medical sociology. The persistence of the association over time and its generality across very different places suggests that no fixed set of intervening risk and protective factors can account for the connection. Instead, fundamental-cause theory views SES-related resources of knowledge, money, power, prestige, and beneficial social connections as flexible resources that allow people to avoid risks and adopt protective strategies no matter what the risk and protective factors are in a given place or time. Recently, however, intelligence has been proposed as an alternative flexible resource that could fully account for the association between SES and health and thereby find its place as the epidemiologists' "elusive fundamental cause" (Gottfredson 2004). We examine the direct effects of intelligence test scores and adult SES in two data sets containing measures of intelligence, SES, and health. In analyses of prospective data. (Contains 1 figure, 2 tables, and 3 notes.)