In the latter part of the 1990's, testing for Chlamydia trachomatis and Neisseria gonorrhoeae infections was revolutionized by the introduction of nucleic acid amplification tests (NAATs) which achieve greater sensitivity than traditional culture methods by exponentially replicating the nucleic acid of these organisms. The specimens collected for NAATs are easier to transport and NAATs permit collection of less invasive specimens for testing (i.e. voided urine or patient-collected vaginal swabs for women rather than urethral or endocervical swabs). Despite their somewhat higher costs, these tests have been found to be preferred by patients (because specimens can be collected less invasively), by clinicians (because of both their ease of collection and increased sensitivity), and to permit expanded screening both in traditional clinical settings and at outreach sites where testing has not typically been done in the past.