In planning health protection for pregnant as well as nonpregnant women exposed to fluorides, information about their fluoride metabolism is essential. The authors determined fluoride balances in small groups of young women maintained on two different low-fluoride diets for one or two 21-day periods in a metabolic unit. One diet contained an average of 0.41 mg F/day, and the other contained an average of 0.27 mg F/day. Excretion of fluoride in pooled three-day collections for each subject was about 80% in the urine and 20% in the feces. Pregnant (last half of term) and nonpregnant women demonstrated small negative fluoride balances; the averages were about -0.32 mg F/day and -0.15 mg F/day, respectively. Similar values have been found for young males in other studies. Pregnancy in these subjects did not markedly alter normal fluoride metabolism.