Fluoride (F), over a narrow concentration range, increases bone formation. Aluminum (Ai) too is biphasic in its action on bone, being mitogenic at very low levels and inhibitory at higher levels. Both F and Al are present in finished drinking water where the chemical interaction of these two agents is well characterized. F and AI, given individually, accumulate preferentially in bone. In addition. in vivo studies have shown that F causes the co-accumulation of Al in bone. Thus, it was necessary to determine the interactive effect of these two agents on bone mitogenesis. Calvaria were obtained from neonatal CD-1 mice and cultured with various concentrations of F (0.05~19 ppm) as NaF, Al (2 ppb~2 ppm) as $AlCl_3$ , or F and Al for 3 days at $37^{circ}C$ on a rotating roller drum. Alkaline phosphatase activity in calvaria and $eta$-glucuronidase activity in culture medium were determined as a measures of bone turnover. Alkaline phosphatase activity in calvaria was significantly increased by F (0.05~2 ppm) treatment and $eta$-glucuronidase activity was slightly increased in the culture medium of calvaria treated with 0.3 ppm Al. The combination of 19 ppm F and 0.3 ppm Al increased alkaline phosphatase activity in calvaria, but did not affect $eta$-glucuronidase activity, suggesting the interactive effect of fluoride and aluminum on bone turnover.