Why do some groups retain their ethnicity as they become assimilated into mainstream American life while others do not? This study employs both historical sources and contemporary survey data to explain the seeming paradox of why Japanese Americans have maintained high levels of ethnic community involvement while becoming structurally assimilated. Most traditional approaches to the study of ethnicity in the United States are based on the European immigrant experience and conclude that a zero-sum relationship exists between assimilation and retention of ethnicity: community solidarity...