With the strategy of homologue molecular cloning using the sequence of the maleless gene (mle) of Drosophila, the novel homologous human and mouse genes with longer DNA/RNA helicase box (DEAD/DEAH box), named DDX36 and Ddx36 genes, respectively, were cloned as new members of the DEAD/H box superfamily. The predicted protein encoded by human DDX36 gene has a sequence identity of 37% and similarity of 58% with the MLE protein of Drosophila and 91% and 94% with the predicted protein encoded by mouse Ddx36 gene, respectively. Northern blotting of DDX36 shows a single strong signal of 3.8 kb in the hybridization pattern in human testis but no or very weak signal in other tissues. The DDX36 gene is mapped to chromosome 3q25.1-3q25.2, in which 26 exons and 25 introns have been identified. DDX36 and Ddx36 genes may be involved in sex development, spermatogenesis and male reproduction.