Investigators at the University of Alabama in Birmingham in collaboration with investigators from the Centers for Disease Control in Atlanta are evaluating the performance of three commercial nucleic acid amplification tests for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in pharyngeal and rectal swab specimens. Cultures for C. trachomatis and N. gonorrhoeae are performed as additional reference tests. Study subjects are men and women attending sexually transmitted disease (STD) and HIV care clinics in Birmingham, Alabama, who report sexual behaviors that place them at risk for pharyngeal or rectal sexually transmitted infections.