Dmc1 and Rad51 are eukaryotic RecA homologues that are involved in meiotic recombination. The expression of Dmc1 is limited to meiosis while Rad51 is expressed in mitosis and meiosis. Dmc1 and Rad51 have unique and overlapping functions during meiotic recombination. Here we report the purification of the Dmc1 protein from the budding yeast Saccharomyces cerevisiae and present basic characterization of its biochemical activity. The protein has a weak DNA-dependent ATPase activity and binds both single-strand DNA (ssDNA) and double-strand DNA (dsDNA). Electrophoretic mobility shift assays suggest that DNA binding by Dmc1 is cooperative. Dmc1 renatures linearized plasmid DNA with first order reaction kinetics and without requiring added nucleotide cofactor. In addition, Dmc1 catalyzes strand assimilation of single strand DNA oligonucleotides into homologous supercoiled duplex DNA in a reaction promoted by ATP or the non-hydrolyzable ATP analog AMP-PNP.