This study examines the relationtship betweeni acculturation anid famtnily funictioninig in families of Mexican descent. Using a family s)stemns fraflmework, faiiii funictiotiiig is defined in terms of internal versus extrernalfameilv activitiies. Accultluratioln is defined by generational statu.s, language preferentcelproficienicy, aid letgtgh of-residence. Forty-five families were selected from Head Start programns aid placed ilto three groups-unacculturated, moderately acctulturated, and acctiltturated. Thte notherandfathlerof each famnily were interviewed and adminiistered a socio-demnographic questionnaire anid the Family Environment Scale (FES). Results gemierally support the stated hypolheses: As families of Mexicani descenti acculturate, they become increasingly involved with social systems outside the family while the basic in1terntal family system remains essenltially untchanged. These findings are discussed as they pettaini to diffrenest models of acculturationz and puiblic policy issues.