Our hypothesis is that nucleic acid amplification testing (NAAT) with the APTIMA Combo2 (AC2) will have greater sensitivity than culture in detecting Neisseria gonorrhoeae in rectal samples. We also hypothesize that AC2 will be equivalent to NAAT with the Becton Dickinson ProbeTec in detecting Chlamydia trachomatis and Neisseria gonorrhoeae in rectal samples.