Medicine theft is a leading cause of inadequate healthcare. Audits of public health procurement suggest that up to a third of medicines go missing in several low income countries, disproportionately affecting those with higher health risk and poverty. In an experiment with the Malawi Ministry of Health, we employ novel measurement strategies and an experiment to determine the pattern of corruption and the effect of a policy response designed to increase the visibility of theft. We placed tracking devices on 2,400 medicine deliveries that could observe their positions in real time. We assigned some medicines with messages about monitoring and the consequences of theft. Using these data, we provide some of the most comprehensive estimates to-date on the scale and consequences of medicine theft. We show that corrupt actors appear to select less observed sections of procurement networks and locations more proximate to smuggling routes. We also show that measures of theft are strongly correlated with patients’ ability to access needed medicines from government clinics. Despite this, we estimate only small effects of our visibility treatment. Evidence from surveys with patients and public health officials suggest these small effects of greater visibility may be due to systematic weaknesses in institutional accountability mechanisms and efforts by public officials to circumvent digital auditing activities. We suggest that digital tracking technologies can be an important tool in preventing theft, especially in combination with efforts to bolster institutional mechanisms of accountability. Read more about our baseline data collection findings in this blog post.