Mr B, a 60-year-old man with back pain, was not informed of an incidental finding of a renal mass suggestive of cancer on a magnetic resonance imaging scan. Failure and delays in test follow-up are a frequent problem in medicine, occurring in more than 5% of significantly abnormal ambulatory test results. Rather than simply blaming involved clinicians, systems for managing tests need to be reengineered using methods from reliability sciences. These begin with investigations into the systemic causes of the failures, then application of approaches such as heightened situational awareness, closed-loop systems, improved handoffs, just-in-time work, culture and practices of stopping to fix problems, forcing functions and simplification, enhanced visual cues, and cautious use of information technology and redundancy, all while avoiding suboptimization. Emerging test management systems and critical test follow-up recommendations illustrate how applying these principles can enhance this important aspect of patient safety.