The first fluoride varnishes were developed during the 1960s (Duraphat® sodium fluoride varnish) and 1970s (Fluor Protector® silane fluoride varnish) to prolong the contact time between fluoride and enamel. Fluoride varnishes adhere to enamel, and calcium fluoride formed after application acts as a long-term reservoir of fluoride. Currently Duraphat varnish is the most widely used topical fluoride for professional application in Europe, and the use of fluoride varnishes is increasing in the USA. Duraphat varnish has been effective in three decades of clinical studies, but the results of Fluor Protector varnish are inconclusive. The percent caries reductions found in the 1990s have generally been lower than those reported in earlier studies, probably because of the higher exposure to other preventive measures in the more recent studies. In studies comparing Duraphat varnish and APF gel, Duraphat varnish was equally or more effective than APF gel. Sealants were most effective in preventing occlusal caries. Four applications per year, or three weekly applications once a year, have been found to be effective. However, several studies have shown that two applications per year may provide comparable results. Application is fast and easy. Professional prophylaxis is not necessary, and the patient can leave immediately after the treatment. No acute toxicity has been reported after using any fluoride varnish.