The incidence of acute episodes of intestinal infectious diseases in the United States was estimated through analysis of community-based studies and national interview surveys. Their differing results were reconciled by adjusting the study population age distributions in the community-based studies, by excluding those cases that also showed respiratory symptoms, and by accounting for structural differences in the surveys. The reconciliation process provided an estimate of 99 million acute cases of either vomiting or diarrhea, or both, each year in this country, half of which involved more than a full day of restricted activity. The analysis was limited to cases of acute gastrointestinal diseases with vomiting or diarrhea but without respiratory symptoms. Physicians were consulted for 8.2 million illnesses; 250,000 of these required hospitalization. In 1985, hospitalizations incurred $560 million in medical costs and $200 million in lost productivity. Nonhospitalized cases (7.9 million) for which physicians were consulted incurred $690 million in medical costs and $2.06 billion in lost productivity. More than 90 million cases for which no physician was consulted cost an estimated $19.5 billion in lost productivity. The estimates excluded such costs as death, pain and suffering, lost leisure time, financial losses to food establishments, and legal expenses. According to these estimates, medical costs and lost productivity from acute intestinal infectious diseases amount to a minimum of about $23 billion a year in the United States.