The possible association between salivary non-immunoglobulin (lysozyme, lactoferrin, hypothiocyanite, agglutinins) or immunoglobulin (total IgA, anti-Streptococcus mutans IgA) antimicrobial factors, and the prevalence of dental caries was studied in 59 young adults. These antimicrobial factors were also analysed in relation to the salivary levels of mutans streptococci (MS). The amount of MS correlated significantly (+0.31, p less than 0.05) with the number of initial caries lesions (Di) but not with other caries indices (DMFT, DMFS, DS). The group with no Di (N = 17) had significantly (p less than 0.05) more hypothiocyanite (HOSCN/OSCN-) and anti-S. mutans IgA antibodies in whole saliva than those with initial caries lesions (N = 42). None of the antimicrobial factors alone showed any significant association with salivary MS counts. Our results suggest that HOSCN/OSCN- and anti-S. mutans IgA may be involved in the prevention of the early phases of dental caries.