An outbreak of Escherichia coli O157:H7 was investigated in Calgary, Alberta, Canada, after a fourfold increase in laboratory reports was received. The strain of E. coli O157:H7 isolated was unique to North America. Most persons affected reported eating beef donair. Beef donair is a Middle Eatern style dish. It consists of ground beef and spices which are hand packed into large cones on a skewer. Consumption of beef donair from one of two locations of a local restaurant chain was the only statistically significant risk factor for infection. No samples of the implicated ground beef were available for microbiological testing. The beef donair had been held at temperatures which would have promoted bacterial growth, cooking temperatures were not checked, and partially cooked meat juices could have contaminated ready to eat foods. One employee was infected. The beef served had come from one, unnamed, supplier. This supplier obtained beef from many suppliers. Since records were poor, the specific origen of the beef was not determined.