Competency assessment is critical for laboratory operations and is mandated by the Clinical Laboratory Improvement Amendments of 1988. However, no previous reports describe methods for assessing competency in patient safety. We developed and implemented a Web-based tool to assess performance of 875 laboratory staff from 29 laboratories in patient safety. Question categories included workplace culture, categorizing error, prioritization of patient safety interventions, strength of specific interventions, and general patient safety concepts. The mean score was 85.0%, with individual scores ranging from 56% to 100% and scores by category from 81.3% to 88.6%. Of the most difficult questions (<72% correct), 6 were about intervention strength, 3 about categorizing error, 1 about workplace culture, and 1 about prioritization of interventions. Of the 13 questions about intervention strength, 6 (46%) were in the lowest quartile, suggesting that this may be a difficult topic for laboratory technologists. Computer-based competency assessments help laboratories identify topics for continuing education in patient safety.