Observational studies have found mixed results on the impact of jail-based chlamydia screen-and-treat programs on community prevalence. In the absence of controlled trials or prospectively designed studies, dynamic mathematical models that incorporate movements in and out of jail and sexual contacts (including disease transmission) can provide useful information. We explored the impact of jail-based chlamydia screening on a hypothetical community's prevalence with a deterministic compartmental model focusing on heterosexual transmission. Parameter values were obtained from the published literature. Two analyses were conducted. One used national values (large community); the other used values reported among African Americans--the population with the highest incarceration rates and chlamydia burden (small community). A comprehensive sensitivity analysis was carried out. For the large-community analysis, chlamydia prevalence decreased by 13% (from 2.3% to 2.0%), and based on the ranges of parameter values (including screening coverage of 10%-100% and a postscreening treatment rate of 50%-100%) used in the sensitivity analysis, this decrease ranged from 0.1% to 58%. For the small-community analysis, chlamydia prevalence decreased by 54% (from 4.6% to 2.1%). Jail-based chlamydia screen-and-treat programs have the potential to reduce chlamydia prevalence in communities with high incarceration rates. However, the magnitude of this potential decrease is subject to considerable uncertainty.