The principal objective of this study was to investigate the long-term (35-36 years) effects of a K-3 bilingual-multicultural programme by studying the former Mexican-American participants and controls as adults in their 30s and 40s. The controls were enrolled in an English immersion programme and were matched to the experimental programme participants in terms of ethnicity, generation level and SES; attendance at the same school; and residence in the same community. The two groups were compared on WRAT-3 achievement scores, high school graduation rates, fluency in English and Spanish, cultural values and on reported multicultural participation. A small sample of participants from each of the groups also participated in intensive interviews to assess their opinions about Proposition 227, bilingualism and recent immigrants from Mexico. Our data supported the findings of previous long-term bilingual programme effectiveness studies that showed that two-way/maintenance programmes are related to long-term academic achievement, increased high school graduation rates and do not delay Americanisation or interfere with academic performance in English. All participants, regardless of group, opposed Proposition 227 and viewed new immigrants as positively impacting their communities. They also perceived bilingualism as an asset contributing to their quality of life. (Contains 4 tables.)