Only around a half of the African children who need HIV treatment are getting it. Without anti-retroviral therapy, most will die within five years. The ARROW trial looked at the same question as DART, but in children, following more than a thousand participants over five years. The results once again showed no benefit at all to using laboratory monitoring to check for side effects, and only a small extra benefit to monitoring treatment with CD4 tests to detect early treatment failure. The results strongly suggest that prioritising medicines for all the children who need them will save many more lives than investing in the expensive lab tests used for monitoring by many programs.