In 1998, an outbreak of Campylobacter jejuni infections occurred in Kansas among persons attending a school luncheon; community cases were also reported. In a cohort study of luncheon attendees, 27 (17%) of 161 persons reported illness. Consuming gravy (relative risk [RR], 4.2; 95% confidence interval [CI], 1.5-11.7) or pineapple (RR, 2.4; 95% CI, 1.0-5.7) was associated with illness. Both foods were prepared in a kitchen that served 6 other schools where no illness was reported. A cafeteria worker at the luncheon had a diarrheal illness and was the likely source of the outbreak. The pulsed-field gel electrophoresis (PFGE) patterns of the isolates from the food handler and those of 8 lunch attendees were indistinguishable. Isolates from 4 community patients differed. This was the first use of PFGE in a Campylobacter outbreak in the United States; its use was critical in determining that community cases were not linked.