ABSTRACT NIAAA identifies underage drinking as a public health issue with serious consequences. Lesbian, gay, and bisexual (LGB) youth who use alcohol have even worse consequences, such as increased risk of cancer, risky sexual behavior, and suicidal attempts. Hispanic LGB youth may be at even greater risk of developing alcohol use problems because of the additive status-based social stressors that may arise. Stress theories posit that youth who experience stressful events cope with psychological distress by using alcohol. To date, little is known about how Hispanic LGB youth respond to social stressors or how socio-cultural protective factors (i.e., coping strategies, social support) and negative and positive affect may mediate these stressors’ effects on Hispanic LGB youth’s use of alcohol. EMA is a unique method that can assess stress theories, psychological distress, and alcohol use in real-time, however it has not been used to assess this relationship with Hispanic LGB youth. The research aims of this Career Development Award (K08) are to: 1) Assess the acceptability and feasibility of social stressors, alcohol, and protective factor measures in ecological momentary assessment (EMA) between Hispanic and white LGB youth; 2) Examine the effects of social stress on LGB youth’s alcohol use and the mediating effects of affect; and 3) Examine the sociocultural risk and protective factors of alcohol use. This study will be conducted in 3 phases. In Phase 1, the measures will be developed using cognitive interviews with Hispanic and white LGB youth (N=20 or until saturation is reached). Phase 2 will consist of a pilot-EMA testing of the EMA with Hispanic and white LGB youth (N=20) over two-weeks and post- EMA cognitive interviews to assess the feasibility and acceptability of the EMA. In phase 3, the finalized EMA will be conducted over a 30-day period to assess social stressors, affect, and sociocultural protective factors of alcohol use among 50 Hispanic and 50 white LGB youth. This K08 proposed study and mentor plan will help the candidate develop expertise in 1) The development and progression of alcohol use in youth; 2) Risk and protective factors of alcohol use in LGB youth; 3) Ecological Momentary Assessment (EMA) methodologies; 4) Intensive longitudinal data analysis for analyzing EMA; and 5) cultural adaptation of measures and interventions for LGB youth. The training goals will build off the candidate’s prior training in 1) Positive youth development; 2) The effects of social stressors on substance use; 3) qualitative analysis, and 4) advanced statistical analysis.