To determine whether asking general practitioners to offer chlamydia screening at the same time as Pap screening increases chlamydia screening rates.

A pragmatic cluster randomised controlled trial.

Doctors from 31 general practices in the Australian Capital Territory performing more than 15 Pap smear screens per year, and all women aged 16–39 years attending those practitioners between 1 November 2004 and 31 October 2005.

Doctors in the intervention practices were asked to routinely offer combined chlamydia and Pap screening to eligible women; doctors in the control practices were asked to implement screening guidelines based on a risk assessment of the individual patient (ie, usual practice).

Chlamydia screening rate per visit.

There were 26 876 visits by eligible women during the study period: 16 082 to intervention practices and 10 794 to control practices. Chlamydia screening occurred during 6.9% (95% CI, 6.5%–7.3%) of visits to intervention practices and 4.5% (95% CI, 4.1%–4.9%) of visits to control practices. After controlling for clustering and potential confounders, there were twofold greater odds of chlamydia screening occurring during a visit by an eligible woman to an intervention practice than to a control practice (adjusted odds ratio, 2.1 [95% CI, 1.3–3.4]).

Combining chlamydia and Pap screening increases the rate of chlamydia screening in general practice. Implementing this approach would require little additional infrastructure support in settings where a cervical screening program already exists.