The influence of diet and fluoride on odontogenesis in rats was investigated. 20 foetuses, 20 days old, were divided into four groups. The control group was fed with the standard diet and drank water with 0.16 mg F/l. The second, third and fourth groups were fed with the deficit, experimental diet and drank distilled water with 10 and 110 mg of natrium fluoride per litre or without fluoride. In each group, the observed tooth-bud development assumed different stages. The less advanced cap stage assumed the tooth-bud in the group fed with the deficit diet and given distilled water without fluoride. In the remaining groups, the development of observed first molars in mandible assumed the different level of its advancement in the same stage of odontogenesis – bell stage