OBJECTIVE: To describe the frequency of the 3-month test for re-infection among sexual health service patients in Australia. METHODS: We assessed the re-testing rates at 30-120 days after chlamydia infection in men who have sex with men (MSM), heterosexual males and females attending sexual health services across Australia between 2004 and 2008. A chi(2)-test was used to determine significant differences in re-testing rates according to demographic characteristics and trends over time. RESULTS: In the 5-year period, 10207 MSM, 28530 heterosexual males and 31190 heterosexual females were tested for chlamydia. Of those tested, 9057 (13.0%) were positive. The proportion of patients with chlamydia infection who were re-tested in 30-120 days was 8.6% in MSM, 11.9% in heterosexual males and 17.8% in heterosexual females. Among MSM, chlamydia re-testing rates were lower in men aged /=30 years (12.5%) (P=0.04) and lower in travellers and migrants (2.9%) than non-travellers (9.9%) (P=0.002). In heterosexual males, chlamydia re-testing rates were lower in men in regional and rural areas (10.5%) than metropolitan areas (13.5%) (P=0.017). There was no increasing trend in re-testing rates between 2004 and 2008 (P=0.787). Of the patients re-tested, 44.1% of MSM were positive, 21.0% of heterosexual males and 16.1% of females. DISCUSSION: The high chlamydia positivity at 30-120 days support recommendations that call for a 3-month test for re-infection following a positive test. The low re-testing rates highlight the need for innovative strategies to increase re-testing.