The sensitivity of Roche Cobas Amplicor Chlamydia trachomatis polymerase chain reaction (PCR) including the internal control (IC) programme to identify inhibition, was investigated on 3 different samples from women: (1) swab samples from the urethra and the cervix pooled in 2-SP transport medium, (2) swab sample from the cervix transported in a urine sample from the same patient, and (3) urine sample alone. Out of the 2412 patients, 193 (8.0%) were chlamydia positive and in 14 of these the results showed discrepancies between sampling methods. The sensitivity of PCR on urethra/cervix, urine/cervix and urine was 98.4% (190/193), 97.9% (189/193) and 93.3% (180/193) respectively. The higher sensitivity of PCR on urethra/cervix and urine/cervix as compared with urine alone was statistically significant. Without the IC, the sensitivity of PCR on urethra/ cervix, urine/cervix and urine would have been 95.9% (185/193), 94.8% (183/193) and 90.7% (175/193) respectively. Factors influencing the rate of inhibition were also studied.