Abstract.Sterile polished slabs of bovine enamel, mounted in small acrylic cylinders, were held in the mouth for 2 hours. The acquired pellicles deposited on the enamel surfaces were examined insituon the slabs or after transfer to microscope slides. Indirect immunofluorescent stainingin situafforded positive identification of IgA and lysozyme in pellicles. The preferred technique required acid separation of the pellicle from the enamel, transfer to a microscope slide, and fixation in cold ethanol. Histochemically, this pellicle appeared to he predominantly basic. Results of indirect immunofluorescent tracing indicated that IgA and lysozyme were regular constituents of the pellicle, amylase and IgG were less consistently detected, and albumin and fibrinogen were rarely encountered.