Although many observers have drawn attention to the low levels of trust in physicians among members of racial/ethnic minorities and those of lower socioeconomic status, the reasons for this mistrust are not well understood. Using a social distance perspective and a large, nationally representative data set, I find that blacks and Hispanics are less trusting of their personal physicians than are whites and that education and income both increase physician trust. A fraction of each of these differences can be explained by physicians' behavior (the perceived thoroughness of the last examination, how well the physician listened, and how well the physician explained), but most of each difference remains well after physicians' behavior is held constant. The otherwise positive, strong effect of physicians' behavior has only a limited capacity to explain these differences because social distance moderates the strength of the effect of that behavior. For blacks, Hispanics, and those of lower socioeconomic status, physicians' behavior exerts much less effect on trust than for whites and those of higher socioeconomic status. A social distance perspective helps to explain this downweighting, as well as the divergent ways in which different sociodemographic groups evaluate physicians. By understanding the inference of trust as a social cognitive process, scholars can understand more clearly why some groups are more receptive to physicians than others, and why some groups' mistrust is more resistant to updating. (Contains 4 tables and 7 footnotes.)