Introduction National guidelines recommend opportunistic chlamydia screening of sexually active 16- to 29-year-olds and encourage retesting 3–12 months after a diagnosed chlamydia (Chlamydia trachomatis) infection. We assessed chlamydia testing patterns at five Australian family planning clinics (FPCs). Methods: Using routine clinic data from 16- to 29-year-olds, we calculated chlamydia testing and positivity rates in 2008–2009. Reattendance, retesting and positivity rates at retesting within 1.5–4 and 1.5–12 months of a positive result were calculated. Results: Over 2 years, 13 690 individuals aged 16–29 years attended five FPCs (93% female). In 2008, 3159 females (41.4%,) and 263 males (57.0%) were tested for chlamydia; positivity was 8% and 19%, respectively. In 2009, 3178 females (39.6%) and 295 males (57.2%) were tested; positivity was 8% and 23%, respectively. Of 7637 females attending in 2008, 38% also attended in 2009, of which 20% were tested both years. Within 1.5–4 months of a positive test, 83 (31.1%) females reattended; the retesting rate was 13% and 12% retested positive. Within 1.5–12 months of a positive test, 96 (57.5%) females reattended; the retesting rate was 36% and 13% retested positive. Conclusions: Approximately 40% of young people attending FPCs were tested for chlamydia but a smaller proportion were tested annually or were retested following chlamydia infection. High positivity rates emphasise that FPCs see a high-risk population. To maximise testing opportunities, clinical prompts, patient reminder systems and non-clinic testing strategies may be needed.