A Clostridium perfringens gastroenteritis outbreak occurred among employees of a Connecticut factory. Although the same foods were served, banquet style to all three shifts, the attack rate was almost twice as high for those who ate on the day shift, than for those on the evening shift or night shift. Among employees of the day shift, attack rates were highest for those who ate during the first 30 minutes of the 2.5-hour day shift serving period and decreased throughout the serving period. The one-hour evening shift serving period had a similar trend toward higher attack rates earlier in the serving period. Stratified analysis indicated that gravy was the likely vehicle. The decreasing attack rate pattern within serving periods occurred only for those who ate gravy. The gravy had been prepared 12–24 hours in advance of banquet service. It had been improperly cooled and was reheated shortly before and throughout the serving periods. Persons who ate gravy that had been reheated for the longest period of time had the lowest attack rate, probably because they were exposed to a lower concentration of organisms.