314 African American, 434 U.S. Caucasian, and 398 U.S. Hispanic individuals were typed at X STR markers DXS6795, DXS9902, DXS8378, DXS7132, DXS6803, DXS6789, DXS7424, DXS101, GATA172D05, DXS7130, GATA165B12, HPRTB, GATA31E08, DXS10147, DXS7423. High forensic efficiency parameter values confirm the potential usefulness of these markers in certain specific kinship situations involving female offspring as well as identity testing. Alleles previously unobserved in U.S. populations were noted in this study at 8 different markers. Additionally, null alleles and a triallelic pattern were observed and described. Pairwise comparisons indicated consistency with similar published populations at overlapping markers. These data represent a substantial increase in the quantity of U.S. X chromosomal short tandem repeat data available to the community.