Young men having sex with men (YMSM) are the fastest growing HIV+ population worldwide. Thailand has the highest adult HIV seroprevalence in Asia; 28.6% of men having sex with men in Bangkok are HIV+. The HIV incidence rate among YMSM in Bangkok is 12.2 per 100 person-years. Effective prevention strategies are urgently needed to prevent HIV transmission in this high-risk population. Pre-exposure prophylaxis (PrEP) is an efficacious HIV prevention strategy recommended by the CDC and WHO for all at-risk individuals, including HIV-negative MSM. PrEP is highly effective when taken as prescribed, but PrEP utilization has been low and adherence is often inadequate. To address these challenges among Thai YMSM, we propose to develop a technology facilitated intervention combining Motivational Enhancement System for PrEP Uptake and Adherence (MES-PrEP) and Motivational Interactive Text Messaging (MTM) to increase uptake of and sustained adherence to PrEP among HIV-negative, Thai YMSM. MTM will be programmed and tested to send two-way motivational messages to promote PrEP uptake and adherence. Our primary aim is to develop and pilot test MES-PrEP and MTM and associated protocols and to assess preliminary evidence of the effect of the technology facilitated intervention. The proposed study includes 3 phases. Phase I includes in-depth interviews with 30 HIV-negative Thai YMSM to explore barriers and facilitators of PrEP initiation and adherence to inform intervention content. Phase II consists of adapting and beta testing MES-PrEP and MTM for functionality and feasibility using 10 HIV-negative Thai YMSM. In Phase III, we will conduct a pilot randomized controlled trial to evaluate the feasibility, acceptability, and preliminary efficacy of MAS-PrEP and MTM to increase PrEP uptake and adherence among Thai YMSM. We will enroll 60 HIV-negative Thai YMSM who have not started PrEP and 60 YMSM who are on PrEP but not adherent to it. Participants will be randomized 2:1 to received MES-PrEP and MTM (n=40) or Standard PrEP Counseling (n=20). Feasibility and acceptability of the intervention will be assessed through paradata of usage patterns and the System Usability Scale. Preliminary impact will be assessed by evaluating the proportion of PrEP initiation and level of adherence to PrEP. Participants will complete the assessments at baseline and 1, 3, and 6 months post- intervention. Biomarkers of adherence to PrEP and HIV/STI will be collected. Upon project completion, we shall have developed a highly innovative mHealth intervention to support MSM using PrEP which will be ready for testing in a larger efficacy trial.