Research on core cultural values has been central to behavioral and clinical research in ethnic groups. "Familismo" is one such construct, theorized as the strong identification and attachment of Hispanic persons with their nuclear and extended families. Our anthropological research on this concept among Mexicans and Mexican immigrants in the United States elaborates the concept, and promotes greater complementarity between quantitative and qualitative data on the topic. Ethnographic work spanning 3 sites over four years reveal that "familismo" as expressed in narratives is a more contested and evocative concept than most quantitative and behavioral literatures tend to suggest. By suggesting that when "familismo" is used in generalizing ways, it neglects the broader significance of nostalgia or of a larger social (extra-familial) connectedness, we do not ignore the need for population-based research. Instead, we hope to forward and crystallize studies of culture change in migrants and to sustain a complementary and simultaneous conversation based on contextual and qualitative data. (Contains 2 tables and 8 notes.)