Infections of the mouth are mostly local in nature, but if left untreated, may lead to potentially life-threatening conditions. Mouth infections, such as caries, pulpitis, periodontal disease, and oral mucosal infections, such as mouth ulcers, are readily accessible and thus well suited to photodynamic therapy (PDT). Many organisms, which may cause infections in the oral cavity, have been found to be susceptible to PDT to varying degrees. Several photosensitizers have been shown to be effective against target organisms without inducing damage to the host tissues. The use of appropriate photosensitizers and light doses can eradicate virtually all organisms in the region, but in the oral cavity where there is a balance of native microflora, this would potentially be a problem leading to the overgrowth of opportunistic organisms. This may be overcome using a photosensitizer linked to an antibody recognizing the target organisms. At present, treatment of infections with PDT appears best for localized and superficial infections. Treatment of deeply seated infections, such as abscesses, may also be possible with improvements in the delivery of the sensitizer and light. PDT has the potential to become established as an alternative antimicrobial approach for oral infections and deserves further evaluation.