We tested three competing hypotheses regarding the adult "Hispanic mortality paradox": data artifact, migration, and cultural or social buffering effects. On the basis of a series of parametric hazard models estimated on nine years of mortality follow-up data, our results suggest that the "Hispanic" mortality advantage is a feature found only among foreign-born Mexicans and foreign-born Hispanics other than Cubans or Puerto Ricans. Our analysis suggests that the foreign-born Mexican advantage can be attributed to return migration, or the "salmon-bias" effect. However, we were unable to account for the mortality advantage observed among other foreign-born Hispanics.