Luteolin is a flavonoid that exists in a glycosylated form in celery and green pepper. Flavonoids possess antioxidant and anti-inflammatory properties and can reduce the expression of key inflammatory molecules in macrophages and monocytes. It has been reported also that some flavonoids have effects on bone metabolism. The effects of luteolin on the function of osteoblasts were investigated by measuring cell viability, alkaline phosphatase activity, type I collagen production, osteoprotegerin secretion, Wnt promoter activity, BMP-2 and Runx2 expression and calcified nodule formation. Luteolin has no effects upon osteoblast viability but induced an increase in alkaline phosphatase activity, type I collagen production and a decrease in osteoprotegerin secretion in these cells. Luteolin treatment also upregulated BMP-2 mRNA expression. These results suggest that luteolin may be a regulatory molecule that facilitates the differentiation of osteoblasts.