Diners at an Anoka, Minnesota, restaurant reported gastrointestinal illness in March. A list of recent patrons allowed epidemiologists to establish the extent of the outbreak and the food histories of the ill. A total of ten people were identified as cases. Stool samples from two cases were positive for Clostridium perfringens bacteria that were matched genetically using pulse-field gel electrophoresis. Analysis of the food histories indicated the refried beans as the likely sources of the illness. People who ate the refried beans were nine times more likely to become ill than those who did not have beans. The restaurant was inspected and found to be holding the beans at improper temperatures which could have led to the growth of C. perfringens bacteria.