Relationships between grandparents and grandchildren provide an excellent framework for integrating family theory and family methodology. Systematic differences as a function of age, gender, life expectancy, and health as played out through generations suggest some topics are best studied by disentangling variability between and within families. Using data from 1,345 grandchildren (52% girls, mean age 13.69 years, range 9 to 20) reporting on 3,664 grandparents, we compare results obtained from studying grandparent-grandchild relationships individually and at the family level. Results suggest important predictors of relationship quality at the within-subject and between-subject levels. Future research should more carefully integrate each level into theory and design. (Contains 3 tables.)