The uptake and concentration of fluoride in the tissues of oysters was studied under laboratory conditions. Experimental animals were maintained for up to two months in water fluoride levels of 0.5, 2, 8, 32, and 128 ppm. It was found that oysters did accumulate fluoride at all of the experimental fluoride concentrations except 0.5 ppm which is within the range of natural water fluoride levels. Tissue fluoride levels as high as 100 ppm (dry weight basis) were observed in oysters from 32 ppm water; 30 ppm from 8 ppm water; and 18 ppm from 2 ppm water. Oysters with these higher tissue fluoride concentrations, e.g., 100 and 30 ppm, are believed to represent a potential public health problem if they are consumed in large amounts by the general public.