Eight persons developed botulism after eating at a delicatessen on October 1. All eight case-patients had eaten barbecue stuffed potatoes. An open can of cheese sauce that was used to make the potatoes contained type A botulinum toxin and yielded C. botulinum on culture. The reason why the cheese sauce became contaminated with C. botulinum was not known. A manufacturing error seemed unlikely; more likely was that contamination occurred in the delicatessen after the cheese can was opened. C. botulinum was found on potatoes and cutting boards.