Outbreaks of foodborne illness caused by Clostridium perfringens are not usually the result of intoxication and testing of suspected menu items for colony count can often identify the causative item. We describe a large outbreak at a county correctional facility in which the data suggest that illness by intoxication contributed substantially to the outbreak: 29 out of 108 surveyed cases (26.9%) developed symptoms within 2.5 hr of when meal service began. Inmate testimony further suggests advanced food decay. Bacterial analyses of food samples indicated a smaller population of C. perfringens in the chicken taco meat mixture (<10 CFU/g, enterotoxin positive) compared with other items. Statistical analyses of food history data provided substantially more support for the chicken taco meat mixture as causative (odds ratio = 55.79, 95% confidence interval [19.72, 157.83], p < .001) than other menu items. Environmental investigation and testimony from inmates provided additional support implicating the chicken taco meat mixture.