OBJECTIVE. The objective of this study was to determine whether the installation of equipment for diaper-changing, hand-washing, and food preparation that is specifically designed to reduce the transmission of infectious agents would result in a decrease in the rate of diarrheal illness among children and their teachers in child care centers. METHODS. Twenty-three pairs of child care centers were matched on size and star-rated license level. One member of each pair was randomly assigned to an intervention group and the other to a control group. Intervention centers received new diaper-changing, hand-washing, and food-preparation equipment, and both intervention and control centers received hygiene and sanitation training with reinforcement and follow-up as needed. Families with children in participating classrooms were called biweekly to ascertain the frequency and severity of any diarrheal illness episodes. Staff attendance was monitored, and staff hygiene and sanitation behaviors were observed and recorded monthly. RESULTS. Although hygiene and sanitation behaviors improved in both intervention and control centers, there was a significant difference favoring the intervention centers with respect to frequency of diarrheal illness (0.90 vs 1.58 illnesses per 100 child-days in control centers) and proportion of days ill as a result of diarrhea (4.0% vs 5.0% in control centers) among the children. Staff in those same classrooms were reported to have a significantly lower proportion of days absent as a result of any illness (0.77% in treatment centers versus 1.73% in control centers). CONCLUSION. Diapering, hand-washing, and food-preparation equipment that is specifically designed to reduce the spread of infectious agents significantly reduced diarrheal illness among the children and absence as a result of illness among staff in out-of-home child care centers.