Obox6 is a member of the Obox (oocyte-specific homeobox) gene family. The Obox6 gene was isolated from the mouse two-cell embryonic cDNA library. Using reverse transcriptase-polymerase chain reaction analysis, we found Obox6 is expressed exclusively in early embryonic stages and exhibits an elevated expression from the two-cell stage to the morula stage. The gene is thought to be involved in early embryogenesis. To study the function of Obox6 in early embryogenesis, we generated Obox6 mutant mice using a gene targeting strategy. Obox6 mutant mice with genetic background of C57BL/6J inbred were born according to Mendelian rules without apparent defects. The mutant mice grew without morphological abnormalities and with normal fertility. The lack of an obvious phenotype in Obox6-null mice and altered RNA levels of some Obox genes raise the possibility that other members of the Obox gene family can compensate for Obox6 function during embryogenesis.