Fifty Afrikaner heifers maintained under ordinary veld conditions were divided into five groups. Each group received 5, 8 or 12 ppm fluorine in the drinking water and in addition three groups also received defluorinated superphosphate. The heifers were kept over four breeding seasons, during the first two of which they were served naturally and during the last two by artificial insemination. Breeding records were kept for each animal. Reproduction was normal in all groups during the first season; during the second season there was an increase in post-calving anoestrus in the groups receiving 8 and 12 ppm fluorine. During the last two seasons there was a progressive decrease in breeding efficiency, in all groups, which was most marked in those receiving the highest levels of fluorine. The addition of the superphosphate appeared to aggravate the harmful effects of fluorine. There was no evidence of a decline in health of the animals, although mottling and pitting of the teeth became progressively worse.