As part of an ongoing project to learn more about what we've got wrong to help us improve, I look at the Therac-25 incidents, a devastating collection of software failures that often rank in the top 10 of civilian radiation accidents. The Therac-25 radiation therapy device killed or injured 6 people across Canada and the United States. The Therac-25 was a room-sized machine, in this cut-away, you can see the computer terminal in the near-bottom left. I look into two of the most severe bugs. Why the manufacturer didn't fix them and what we can learn from their mistakes. The MP3 (Audio) file is available here .