OBJECTIVE: Physician office laboratory regulations may decrease test availability. We examined the potential effects of regulations on test availability and whether the use of tests in diagnosing uncomplicated urinary tract infections is related to availability. STUDY DESIGN: We performed an analysis of a cross-sectional survey conducted in 1994 and 1995. Test availability and use were determined by physicians' reports. POPULATION: The survey respondents included practicing physicians in 3 specialties (family medicine, general internal medicine, and obstetrics and gynecology) from 4 states: Pennsylvania (which had longstanding office laboratory regulations), and Alabama, Minnesota, and Nebraska (states that were not regulated until the implementation of the Clinical Laboratory Improvement Amendment of 1988). OUTCOMES MEASURED: We determined whether 4 specific tests were available in the office and how the tests were used to diagnose uncomplicated urinary tract infections. RESULTS: Our analysis was based on the responses from the 1898 respondents to the survey. All tests were less commonly available in Pennsylvania; this included the dipstick, microscopic urinalysis, wet prep, and urine culture (odds ratio [OR]=0.20-0.34; all P values < .05). The availability of the microscopic urinalysis and culture increased their use (OR = 4.37 and 2.03, respectively; P=.001). The availability of microscopic urinalysis was associated with a decrease in ordering urine cultures (OR=0.42; P=.001), and the availability of the dipstick was associated with a decrease in the use of both the microscopic urinalysis (OR=0.36; P=.02) and the culture (OR=0.48; P=.05). CONCLUSIONS: We found lower test availability in the state with office laboratory regulations and a decrease in testing when availability is reduced, suggesting that laboratory regulations may influence physicians&rsquo diagnostic approach to urinary tract infections. Further study will be required to determine the level of testing that maximizes patient welfare.