To combat dental caries, a chemical has been sought that possesses stronger antimicrobial properties than fluoride in support of its physicochemical tooth-protecting properties. These searches have led to several agents, of which chlorhexidine (CH) appears most effective. To reduce local side effects of the well-known 0.2% CH mouthwash, a 0.05% CH gluconate + 0.04% NaF solution, pH 5.9, has been developed. Use of this combination over a 2-year period resulted in a 53% reduction in caries increment and a 75% reduction in gingival bleeding, i.e. a clear duality of prevention of oral disease (Luoma et al. 1978). Staining of teeth was minimal and easily removable in about one third of the subjects. To lessen the contribution of patients, chlorhexidine gels, without but more especially with fluoride have been professionally administered. Reductions in salivary mutans streptococci after short periods of gel applications have been found to persist longer than reductions after brief periods of mouthwashing. Reductions of approximal caries increment by about 50% in children, and root surface caries in adults have been obtained through use of CH gels. The effect on root surface caries in adults was equal to that obtained through use of local fluoride applications. Dental CH varnish seems promising, especially because a very short contact time with a tooth may be sufficient to reduce mutans streptococci. No simultaneous effects against caries and gingivitis of CH gels or varnishes has been reported. Comparisons of CH solutions, gels and varnishes, with or without fluoride, in relation to their potentials for preventing oral disease in subjects at risk remain to be accomplished.