An Anoka County, Minnesota, restaurant owner received a complaint of gastrointestinal illness among people who ate a 12 foot club party submarine sandwich at a birthday party on June 5. Ingredients in the submarine sandwich included bologna, salami, ham, lettuce, tomato, cheese, peppers, and mayonnaise. The complainant stated that nine people were ill, however contact information was available for only five ill persons. The complainant refused to give contact information for the people who attended the party and remained well. All five attendees interviewed met the case definition. All five (100%) reported diarrhea, two (40%) reported cramps, and one (20%) reported vomiting. The median incubation was 16 hours (range, 10 to 22 hours) and the median duration of illness was 17 hours (range, 10 to 27 hours). The clinical characteristics of this outbreak were consistent with gastroenteritis due to Clostridium perfringens intoxication. The meat ingredients of the submarine sandwich were a plausible vehicle for C. perfringens, however, no food vehicle could be statistically implicated.