The morphological appearance of human enamel treated with topical fluoride (F) agents was studied. Maxillary acrylic appliances carrying the enamel sections were worn for 24 h following 5-min application of neutral NaF gel-drops, APF gel and Duraphat varnish. All F treatment induced surface coatings composed of globules, suggestive of CaF2. The sizes of the globules varied according to the F agents and, in general, were less than 1 micron in diameter. The globules formed following neutral NaF gel-drops and APF were spherical; while those produced by Duraphat were flattened, forming a sheet-like deposit. Irregular masses of organic-like material were seen on F- untreated enamel, which were exposed to the oral environment for 24 h (controls). The prolonged retention of a F-rich surface coating may act as a reservoir of F supplement to the enamel microenvironment, which thus contributes to remineralization.