An outbreak of Clostridium perfringens infections was associated with eating food prepared by an unlicensed caterer and served at a business luncheon. The isolation of Clostridium perfringens from ham suggested that ham was the vehicle of infection. The caterer reported that all foods served were pre-cooked and ready-to-eat. The ham and turkey breasts were transported to the business luncheon in a cooler with ice. Both meats were further sliced onsite, placed in bowls and re-heated in two small non-commercial microwave ovens. Improper reheating and hot holding were suspected.