The remarkable success achieved in cervical cancer prevention is largely attributable to cervical cytology screening, also known as the Papanicolaou (Pap) test. The American Cancer Society (ACS) revised screening guidelines for Pap testing in 2002. The impact of these changes on future numbers of Pap tests has not been assessed. Using National Health Interview Survey (NHIS) data to determine historical screening patterns, we extrapolate the numbers of Pap tests that would be performed through 2010, under 5 different scenarios of implementation of screening guidelines. From 1993 to 2003, there was a steady increase in the number of Pap tests, with an estimated 65.6 million Pap tests performed in 2003. Approximately two thirds of women born after 1930 reported having been screened within the previous year, and 85% within the previous 3 years. Fifteen percent of Pap tests were performed in hysterectomized women, most of whom, according to current guidelines, should not be screened. Based on population projections, if screening behavior remains unchanged, 75 million Pap tests will be performed in 2010. Full compliance with ACS guidelines would approximately halve the total number of tests to 34 million. Potentially, with more appropriate allocation of resources according to guidelines, all women could be screened and the total number of Pap tests reduced, despite projected increases in the population.