Diagnostic tests presently available for Chlamydia trachomatis have widely varying performance characteristics. To assess evolving laboratory testing practices since the introduction of nucleic acid amplification tests (NAAT), we surveyed laboratories in Washington State about their testing practices in 1998 and compared our findings to a similar survey conducted in 1995. Laboratory directors of 61 (87%) of 70 laboratories performing chlamydial tests in 1998 returned a survey. Between 1995 and 1998, 36 laboratories discontinued chlamydial testing, and the total number of laboratories performing tests in the state decreased from 92 to 70, a 24% decline. Of the 36 laboratories that discontinued testing, 25 (69%) had previously used rapid tests. While no laboratory routinely used NAAT in 1995, ligase chain reaction (LCR) was used in 23% of laboratories in 1998 and accounted for 113,624 (36%) of the 318,133 tests performed that year. Among the remaining 204,509 tests performed in 1998, other tests employed included DNA probe (29%), enzyme immunoassay (20%), culture (12%), direct fluorescent antibody assays (3%), and rapid tests (<1%). The majority (65%) of tests performed in 1998 using technologies other than LCR or culture were done in laboratories that did more than 10,000 tests. Cost and loss of revenue to laboratories were the most frequently cited reasons for not adopting NAAT. We conclude that in Washington State, NAAT have been rapidly adopted in larger laboratories, but most patients are still tested with much less sensitive technologies. Financial constraints represent the major barrier to more widespread use of DNA amplification tests.