Among preschool children, we found an association between cytomegalovirus (CMV) infection and salivary immunoglobulin G antibodies to CMV glycoprotein B. All of the 20 infected children had immunoglobulin G to CMV glycoprotein B in their saliva, whereas 38 of 38 uninfected children lacked these antibodies. Testing saliva provides a sensitive and specific alternative to obtaining serum.