Specific objectives include: (1) developing the Mobile Link intervention for young FEWs in Cambodia by conducting participant observation, focus groups and cognitive pilot interviews to produce a bank of 600 theory-informed SMS/VM messages as well as pilot testing the feasibility of collecting data from FEWs through SMS and VMs; 2) evaluating the efficacy of the Mobile Link intervention at the individual and venue level for increasing the uptake of HIV testing, condom use and the utilization of comprehensive SRH care services among 600 sexually-active FEWs through a 12 month, 2-armed RCT and (3) determining the cost-effectiveness of the Mobile Link intervention for FEWs as compared the standard outreach, care and treatment services provided by KHANA.