Each year, millions of persons become ill from foodborne diseases, though many cases are not reported. The Foodborne Diseases Active Surveillance Network (Food-Net), the primary foodborne diseases component of CDC's Emerging Infections Program, was developed to better characterize, understand, and respond to foodborne illnesses in the United States. This report describes FoodNet surveillance data from 1997, the second year of surveillance, and compares findings with data from 1996. The findings demonstrate regional and seasonal differences in the reported incidence of certain bacterial and parasitic diseases and that substantial changes occurred in the incidence of illnesses caused by some pathogens (e.g., Vibrio and Escherichia coli O157:H7) but the overall incidence of illness caused by the seven diseases under surveillance in both years changed little.