A decision analysis model was constructed for comparison of early detection of asymptomatic genital chlamydial infection in women by the direct immunofluorescence antibody (DFA) test and the enzyme-linked immunosorbent assay (ELISA) with no intervention. Early-detection programs using the DFA test and ELISA were shown to be cost-effective in female populations where the prevalences of chlamydial infection exceeded 6% and 7%, respectively. Sensitivity analysis showed that the two most important factors were the probability of developing pelvic inflammatory disease and the cost of the test. The DFA method was more appropriate for an early-detection program because of its higher sensitivity.