The literature is clear that Hispanic immigrants have lower prevalence rates of substance use disorders and other alcohol- and drug-related problems than their U.S.-born counterparts (Grant, Stinson, Hasin, Dawson, Chou, & Anderson, 2004; Maldonado-Molina, Reingle, Jennings, & Prado, 2011). Because Hispanics are a highly heterogeneous group, there are likely to be substantial differences in the prevalence rates in risk behavior between different nationalities of Hispanic adults. For instance, the literature is clear that Mexican Americans and Puerto Ricans have the highest alcohol-related mortality rates among all Hispanic national groups (Caetano, Vaeth, Rodriguez, 2012; Chartier, Vaeth, & Caetano, 2014). Despite the indisputable evidence in support of the “Immigrant Paradox”, in which immigrants have better health outcomes than U.S.-born Hispanics, there is evidence that the corresponding health outcomes of the Hispanic population may depend on the age at which individuals migrate to the U.S (Alegria, 2007; Vega et al., 2004). Several studies have assessed the impact of age of immigration on health outcomes, including psychiatric disorders and illicit drug use. Alegria et al. (2007) found that adults who immigrated to the United States before age 6 had much higher rates of depressive and anxiety disorders. Rates of substance use disorders in general were also higher among those who immigrated earlier (age 6 or younger) compared to those who immigrated at age 7 or older. Using a sample of Mexican Americans, Vega and colleagues (2004) found qualitative differences in immigrants who migrated at age 13 or younger in mood, anxiety and substance use disorders. Other studies have substantiated this link between immigration age and mental health disorders and alcohol use disorders (Alderete, Vega, Kolody, & Aguilar-Gaxiola, 2000). Further, increased duration of residence in the U.S. has been associated with cigarette, alcohol and illicit drug use among Cuban and Nicaraguan youth (Gfroerer & Tan, 2003). In fact, a study by Cheung et al. (2011) found evidence of a “sensitive period” of acculturation in which those who immigrate as a child become more acculturated than adult immigrants, even when living in the U.S. for the same period of time. Therefore, age of immigration seems to have an effect on risk behavior. The proposed mechanism for the relationship between these poor alcohol- and drug-related outcomes among early immigrants is rapid acquisition of normative drinking and drug using behavior that is often modeled by peers native to the United States. This immigration-assimilation effect has been operationalized by generation and viewed as a linear process, where successive generations experience increasingly negative health outcomes (Maldonado-Molina, Reingle, Jennings, & Prado, 2011). However, in light of the developmental research on immigration, culture, and mental health and substance use outcomes, it is likely that Hispanics who immigrated at a very young age are more amenable to the new culture than those who immigrated during their teenage years or later. Immigration to the US at a young age will increase the time in which a person is exposed to the US culture, potentially in a manner similar to those who are born in the US (Alergria, 2007). The exposure to US culture, assimilation, and adoption of American cultural values, has been consistently identified as having poor effects on several dimensions of health (Maldonado-Molina et al., 2011; Alegria et al., 2007; Caetano et al., 2012). Specifically, Caetano and colleagues (2012) suggested that these alcohol-related problems observed among Mexican Americans may be the result of assimilation and acculturation stress, which in turn, leads to increased levels of alcohol consumption. Given the theoretical potential for early immigrants to have cultural exposure levels similar to those who were US born, the purpose of this paper is to systematically determine the age of immigration that puts adults who immigrated at a young age at risk for alcohol- and drug use problems in adulthood. To answer this research question, we used two samples of Mexican Americans residing in two distinct contexts: the U.S.-Mexico border, and cities not proximal to the border. In light of the previous research, we hypothesize that adults who immigrated to the United States prior to adolescence have a qualitatively distinct experience in the U.S. compared to adults who immigrate during late adolescence or adulthood. Developmentally, youth are most vulnerable to social pressures during early adolescence, and the combined stresses of adolescence and acculturation may compound the risk of problematic alcohol and drug use. We expect to observe differences between early immigrants and late immigrants in binge drinking, lifetime alcohol status, number of standard drinks consumed each week, DSM-V Alcohol Use Disorder, and illicit drug use. We also hypothesize that those who immigrate before adolescence have alcohol and drug use behavior that mirrors Mexican American adults who were born in the U.S.-born. Finally, we expect to find differences in alcohol (current drinking status, binge drinking, and number of standard drinks per week) and drug use outcomes by age of immigration, across both the U.S.-Mexico border and non-border contexts. We expect that the age of immigration effect may be greater for alcohol and drug use on the border, as earlier immigration implies longer exposure to the border’s known risk factors for alcohol use and risky behavior (Caetano et al., 2012, 2013; Mills et al., 2012; in press; Office of National Drug Control Policy, 1999). This study is unique in that the population includes a sample of both Mexican Americans living proximal and distal to the U.S.-Mexico border. The U.S.-Mexico border is a unique location, characterized by a high concentration of Mexican Americans, poverty, low education, drug trafficking and related violence (Lusk, Staudt, & Moya, 2012). Alcohol is easily accessible across the border, as the legal drinking age in Mexico is 18; and unlike the U.S., the drinking age is not strictly enforced in Mexico (U.S. Department of State, 2013). Therefore, we are able to compare Mexican Americans living at the border with Mexican Americans living distal to the border, and whether the age of immigration remains a risk factor for alcohol and drug use in both locales.