Because early childhood is an important period for the colonization of bacteria in the primary dentition, it is possible that antimicrobial factors in saliva may modify these early events. In this study we have followed longitudinally 33 children from predentate to dentate phase and analyzed whole saliva for such salivary factors as lysozyme, lactoferrin, salivary peroxidase, myeloperoxidase, thiocyanate, hypothiocyanite, total IgA, IgG, IgM, and total protein. Children's saliva samples were compared with those from an adult reference group whose samples were collected and analyzed in an identical way. It was observed that salivary thiocyanate and IgG increased and salivary peroxidase decreased significantly from predentate to dentate phase. The other parameters remained unchanged. Children in predentate phase already had reached adult levels of hypothiocyanite and IgM, whereas all the other components were found in significantly lower amounts in children's saliva than in adult saliva. Salivary myeloperoxidase assay is interfered by the thiocyanate ions, and the observed increase in salivary "myeloperoxidase" activity may be due to the simultaneous increase in salivary thiocyanate.(ABSTRACT TRUNCATED AT 250 WORDS)