School absenteeism is an inefficient and unspecific metric for measuring community illness and does not provide surveillance during summertime. Web-based biosurveillance of childcare centers may represent a novel way to efficiently monitor illness outbreaks year-round. A web-based biosurveillance program (sickchildcare.org) was created and implemented in 4 childcare centers in a single Michigan county. Childcare providers were trained to report sick children who required exclusion or had parent-reported absences due to illness. Deidentified data on age range, number of illnesses, and illness categories were collected. Weekly electronic reports were sent to the county public health department. Data for reports were gathered beginning in December 2013 and were summarized using descriptive statistics. A total of 385 individual episodes of illness occurred during the study period. Children with reported illness were infants (16%, n = 61), toddlers (38%, n = 148), and preschoolers (46%, n = 176). Illness categories included: fever (30%, n = 116), gastroenteritis (30%, n = 115), influenzalike illness (8%, n = 32), cold without fever (13%, n = 51), rash (7%, n = 26), conjunctivitis (1%, n = 3), ear infection (1%, n = 5), and other (10%, n = 37). The majority of reports were center exclusions (55%, n = 214); others were absences (45%, n = 171). The detection of a gastroenteritis outbreak by web-based surveillance during winter 2013-14 preceded county health reports by 3 weeks; an additional outbreak of hand-foot-mouth disease was detected during June 2014 when standard school-based surveillance was not available. Web-based biosurveillance of illness in childcare centers represents a novel and feasible method to detect disease trends earlier and year-round compared to standard school-based disease surveillance. (author abstract)