BACKGROUND Healthy children attending day-care centers (DCC) may excrete cytomegalovirus (CMV) frequently. Mothers of children excreting CMV are at higher risk for acquiring this infection than mothers of children not excreting CMV. Despite the increased attendance to DCC by children there is a lack of information regarding CMV infection in Mexico. METHODS Prospective determination of CMV excretion in saliva of children attending public and private DCC. Three saliva samples were collected during a 2-month follow-up period from participating children and the presence of CMV was determined by viral culture. Demographic features of children and DCC type were taken into account when comparing children with and without CMV excretion. RESULTS One hundred fifty-two children participated in the study (84 from public and 68 from private DCC). Overall, 17 (11.2%) children excreted CMV during the study period. Excretion rates varied between DCC from 3.1 to 31.3%. Children from private DCC were as likely to excrete CMV as children from public DCC. There were no demographic or clinical features of children associated with viral excretion. CONCLUSIONS CMV was excreted on an average of 11.2% children attending DCC. The type of DCC or other demographic features were not associated with the likelihood of CMV excretion. CMV seronegative mothers of children who attend DCC need to be aware of the possibility of CMV acquisition and transmission in DCC.