OBJECTIVES The objectives of this study were to determine the presenting symptoms, healthcare utilization, and lost time from work and day care associated with acute rotavirus gastroenteritis. METHODS During the winter to spring seasons of 2002-2003 or 2003-2004, children <36 months of age presenting with acute gastroenteritis to urban and suburban pediatric outpatient practices affiliated with 5 academic centers across the United States were enrolled in similarly designed studies. The case definition required >or=3 watery or looser-than-normal stools and/or forceful vomiting within a 24-hour period beginning <or=72 hours before presentation. Stool samples were tested for rotavirus antigen by standard commercial assays. Symptom frequencies for laboratory-confirmed rotavirus and nonrotavirus gastroenteritis were compared by Fisher's exact test; the number of healthcare contacts and lost days from work or day care were compared with the median 2-sample test. RESULTS Stool specimens were obtained from 284 of 303 (94%) participants; 115 (40%) of tested specimens were positive for rotavirus (range, 31-50% across the 5 centers). Compared with participants with nonrotavirus gastroenteritis, children with rotavirus gastroenteritis were more likely to have 1) vomiting (83% versus 66%; P = 0.003), 2) combined diarrhea and vomiting (75% versus 50%; P < 0.001), and 3) fever (60% versus 43%; P = 0.010). More time from work was lost by parents/guardians of children with rotavirus than nonrotavirus gastroenteritis (median 2 versus 0 day; P = 0.007). More day care was missed by children with rotavirus than nonrotavirus gastroenteritis (median 3 versus 1 day; P = 0.002). CONCLUSIONS In this multicenter study, rotavirus consistently caused a sizable proportion of cases of acute gastroenteritis seen in pediatric outpatient practices in the United States during the winter and spring. Rotavirus gastroenteritis was more frequently associated with vomiting, combined diarrhea and vomiting, fever and lost time from work and day care than nonrotavirus gastroenteritis.