The proposed exploratory/developmental study will investigate homophobia/transphobia and other sociocultural factors that influence HIV-related risk behaviors among stigmatized high-risk groups in Malaysia: men who have sex with men (MSM) and male-to-female transgender women (mak nyah). In Malaysia, where the national religion is Islam; homosexuality, transgenderism, and alcohol use are punished among Muslims; and illicit drug use risks severe punishment by law. Through the collaborative efforts among researchers in Malaysia and the U.S. and service providers at the AIDS service organizations (ASOs), we will conduct an exploratory study to prepare future intervention studies to reduce substance abuse and HIV risk behaviors among MSM and mak nyah in Malaysia. Our study team which consists of experienced researchers has ample experience in conducting HIV prevention research for MSM and transgender populations in Malaysia, other Asian countries, and the U.S. The study will provide a solid foundation for understanding homophobia, transphobia, and other significant and meaningful sociocultural factors in relation to substance use and HIV risk behaviors, and will provide a better understanding of the lives of MSM and mak nyah in Malaysia. Based on study findings, our study team will be able to develop substance abuse and HIV prevention intervention studies in the future and recommend policy changes in Malaysia in collaboration with ASOs. The specific aims of the study are: 1) To explore and describe substance use and HIV-related sexual risk behaviors among MSM and mak nyah in Malaysia in relation to background variables; 2) To explore and describe homophobia and transphobia and other sociocultural factors which influence substance use and HIV risk behaviors among MSM and mak nyah in relation to background variables; 3) To explore and determine the theoretical models for future substance abuse and HIV prevention intervention studies specific to MSM and mak nyah; 4) To nurture and sustain the collaborative efforts and build capacity among Malaysian and the U.S. researchers and service providers at ASOs in Malaysia and to lay the groundwork for future substance abuse and HIV prevention intervention studies and programs; 5) To describe the policies and regulations regarding substance abuse and HIV prevention in Malaysia based on key informant interviews, summarize study findings, and recommend future policy changes. Based on purposive sampling, 24 MSM and 24 mak nyah will be recruited for the qualitative interviews. After completion of qualitative analysis, we will recruit 200 MSM and 200 mak nyah for survey interviews based on respondent driven sampling (RDS) methods. Based on mixed methods, we will test the hypotheses and conceptual models. In order to inform future policy changes in substance abuse and HIV prevention in Malaysia, we will also conduct qualitative interviews with 20 key informants. We will sustain our efforts in HIV prevention, health promotion, and human rights improvement for MSM and mak nyah in collaboration with ASOs.