SUMMARYTwo groups of pregnant ewes were given either 1 (control) or 31 (treatment) mg fluoride/1 drinking water. Weekly blood samples were tested for serum fluoride, haematocrit, T3, T4, cortisol, calcium and magnesium. At parturition, serum fluoride was measured in both ewes and lambs. Later, parallel blood and milk samples were taken from ewes and measured for fluoride. Weekly blood samples from the lambs were measured for the same variables, as well as serum phosphate, body weight, bone fluoride and wool production. Serum fluoride in control ewes ranged from 0·6 to 1·9 μmol/1 and in treatment ewes from 8·7 to 35·4/ μmol/1. At birth, serum fluoride of control lambs averaged 0·50 ± 0·042 μmol/1 and of treatment lambs 1·72 ± 0·167 μmol/1. In milk from the control group mean fluoride concentration was 7·11 ± 0·403 μmol/1, and from the treatment group 22·0 ± 1·48 μmol/1. No differences in haematocrit T3, T4, cortisol, calcium or magnesium of ewes were apparent during pregnancy. At birth, body weight of the treatment group lambs was reduced, and T3, calcium and magnesium increased. At 3–4 weeks mean bone fluoride of lambs was higher in the treatment group (580 ± 117 mg/kg) than the control group (105 ± 26·9 mg/kg). After 7 weeks there was an upward trend in serum phosphate of treated lambs, and their wool production (clean fleece weight) at 17 weeks was reduced by 18%, primarily because of decreased staple length.