South Asians are people with origins in India, Pakistan, Bangladesh, Sri Lanka, Nepal, Bhutan, and the Maldives. In the United States (US), South Asians are among the fastest growing ethnic/immigrant groups with a growth rate of 70% from the 2000 to the 2010 Census, now consisting of 1-2% of the total population. California is the state with the largest population of South Asians in the US. South Asians have a genetic tendency towards insulin resistance and central adiposity, increasing their risk for cardiovascular disease (CVD), coronary heart disease, and diabetes mellitus. Immigrants to Western countries may have an amplified risk of CVD due to the adoption of a Western diet and physical inactivity. Two potential social factors that may moderate CVD risk factors among South Asians in the US are acculturation and religiosity. Chapter 1 provides a literature review of acculturation and health, CVD risk factors among South Asians and how they may vary by duration of residence in the US, and religion and health. Conceptual models for the relationships between acculturation and CVD risk factors and between religiosity and obesity are also presented in Chapter 1. Acculturation to American cultural practices has generally been associated with unfavorable changes in CVD risk factors among foreign-born populations. There are few validated measures of acculturation for Asian Americans or South Asians, and acculturation is often operationalized as duration of residence in the US despite problems with this proxy measure. Chapter 2, the first manuscript, examines the validity of acculturation proxy measures, such as duration of residence in the US, with self-reported acculturation measures in validated acculturation scales using the California Asian Indian Tobacco Survey. We found that greater duration of residence in the US, greater percentage of lifetime in the US, and younger age at immigration were associated with more American acculturated responses to the items for South Asian immigrants. We also developed an 11-item acculturation scale for South Asians using existing survey items with an internal consistency reliability of 0.73 and examined the psychometric properties of the scale. Chapter 3, the second manuscript, uses national and state-level cross-sectional data to examine the association of duration of residence in the US with self-reported CVD risk factors among South Asian adults using regression analysis. We found that South Asians immigrants who have resided in the US for greater than 15 years were more likely to be overweight or obese, drink alcohol, eat five or more servings of fruits and vegetables per day, and engage in physical activity compared with more recent immigrants in models adjusting for confounding socio-demographic characteristics, health status, health access, and health behaviors. Age at immigration modified the relationship between duration of residence in the US and body mass index, binge drinking, and alcohol use. Duration of residence was not associated with increased risk for hypertension, high cholesterol, diabetes mellitus, cigarette smoking, fast food intake, or soda intake in adjusted models. Religious involvement has been associated with improved health practices and outcomes. Longitudinal and cross-sectional studies have found lower morality rates, lower prevalence of smoking, and better self-reported health status among individuals who report high levels of religiosity or attend religious services frequently. However, religiosity has also been associated with greater risk of obesity. For South Asians, religiosity and religious participation may be an especially important concept to understand in health promotion because of the dietary restrictions associated with traditional Indian religions and community fellowship for immigrant populations. Chapter 4, the third manuscript, examines the association of religiosity with obesity among a multi-religious group of South Asians in California using regression analysis. We found that high self-identified religiosity was significantly associated with higher BMI after adjusting for socio-demographic and acculturation measures, including the acculturation scale developed in Chapter 2. Highly religious South Asians had 1.53 greater odds (95% CI: 1.18, 2.00) of being overweight or obese than low religiosity immigrants, though this varied by religious affiliation. Religiosity was associated with greater odds of being overweight/obese for Hindus (OR 1.54; 95% CI: 1.08, 2.22) and Sikhs (OR 1.88; 95% CI: 1.07, 3.30), but not for Muslims (OR 0.69; 95% CI: 0.28, 1.70). The findings from this dissertation may provide information on relevant social and cultural norms that may be incorporated in the conceptual model and design of a cardiovascular disease prevention lifestyle change intervention culturally tailored for South Asians in the US.