In this dissertation Mexican American (MA) youths environmental risk contexts, HPA axis functioning and mental health symptomatology were investigated in two separate studies. In the first study, environmental risk contexts were examined utilizing a person-centered approach and focusing on MA adolescents' family, peer, and cultural risk factors in fifth grade (N = 750). Environmental contexts were then linked to mental health symptomatology in seventh grade. Results revealed three distinct environmental contexts: Low risk, Moderate risk-language, and High risk-peer. Youth in the High-risk peer context reported the highest levels of symptomatology; greater major depressive disorder (MDD), anxiety, conduct disorder (CD)/oppositional defiant disorder (ODD), and attention deficit hyperactive disorder (ADHD) symptoms than youth experiencing Low risk or Moderate risk-language context. Females, in particular, experiencing the High risk peer context appeared at greatest risk for MDD symptoms. Finally, adolescents in the Moderate risk-language context displayed similar levels of symptoms to the individuals in the Low risk context, with the exception of higher anxiety. This study suggested that MA youth live in unique environmental contexts and these contexts are differentially related to mental health symptomatology. In the second study, 98 MA youth participated in a three-day diurnal cortisol protocol in hopes of linking perceptions of discrimination and HPA diurnal cortisol rhythms. Results revealed that discrimination was related to greater overall cortisol output and marginally related to the cortisol awakening response and evening levels of cortisol. Results suggest that important physiological processes underlie the experiences of discrimination.