Abstract. In this paper, we extend monotone monomials as large itemsets in association rule mining to monotone DNF formulas. First, we introduce not only the minimum support but also the maximum overlap, which is a new measure how much all pairs of two monomials in a monotone DNF formula commonly cover data. Next, we design the algorithm dnf cover to extract coverings as monotone DNF formulas satisfying both the minimum support and the maximum overlap. In the algorithm dnf cover, first we collect the monomials of which support value is not only more than the minimum support but also less than the minimum support as seeds. Secondly we construct the coverings as monotone DNF formulas, by combining monomials in seeds under the minimum support and the maximum overlap. Finally, we apply the algorithm dnf cover to bacterial culture data.