Results from a clinical trial in five major United States cities show that delivering integrated HIV and substance use disorder (SUD) services using peer navigation in mobile medical units reduced all-cause deaths by 71% compared with those among participants who received peer navigation to community-based services alone. While scientists found no difference in the use of daily, oral preexposure prophylaxis (PrEP) and medication for opioid use disorder (MOUD) between the groups, the secondary outcome of reduced mortality was significant. The study is published in JAMA Psychiatry.