The present study surveyed the ability, the characters and the influential factors on lactobacilli binding to the collagen. The experiment employed reference strains and fresh isolated strains. Binding of 3H-labeled bacteria to human type I collagen absorbed on hydroxyapatite surface (C-HA) was tested. The results suggested that the lactobacilli had high affinity for collagen. Competitive inhibitory assay indicated the attachment was highly specific. Binding to C-HA occurred in a collagen dose-dependent manner. pH value of reaction mixtures significantly affected the adherence. Below pH 6.5, increasing pH value caused a reduction of binding. Above pH 6.5, the binding was less affected. The ionic strength apparently influenced the binding level. The results of this study revealed one of the mechanisms that oral lactobacilli target dentin and root surfaces caries. This may also be a cariogenic virulent factor of lactobacilli.