An investigation of an outbreak of gastroenteritis among people who attended a potluck lunch in September in Portland, was conducted. Illnesses were associated with eating tamales or chicken with mole sauce. Cultures confirmed Clostridium perfringens in tamales and the chicken entrée. Two stool specimens had small numbers of organisms. Pulse field gel electrophoresis identified two C. perfringens subtypes. One subtype occurred in both foods and one stool specimen. The other subtype occurred in the tamales and another stool specimen.