OBJECTIVE: To review available data on genital chlamydial infections in Australia, to determine trends and to make recommendations for improving future data collection. DATA SOURCES: Data are presented from representative laboratories around Australia for the 11-year period 1980-1990. Studies of the prevalence of chlamydial infection in Australia and overseas for the same period were selected for review where relevant epidemiological information (such as patient population, reason for test, demographic data) was available. RESULTS: Overall rates of chlamydial infection from the surveyed laboratories ranged from 3.2%-14.6% for the period 1980-1982 and 2.7%-5.5% for 1990. Rates of diagnosis of Chlamydia appeared to decline in some centres while remaining relatively stable at others. Between 2800 and 4000 cases per year have been reported to the CDI (Communicable Diseases Intelligence) scheme since 1985. Substantial increases in the number of tests performed were seen in nearly all laboratories, reflecting a shift towards screening asymptomatic lower-risk women, however detailed data on the populations tested were unavailable. Studies of prevalence of genital chlamydial infection in Australia revealed highest infection rates among sexually transmitted disease clinic clients (2.5%-14%) and a prevalence of more than 5% in women attending family planning clinics. Studies from overseas showed wide variations in prevalence of infection, from 6% to 28% depending on the populations studied. CONCLUSION: Improved data collection is imperative for assessing the impact of intervention programs for chlamydial infection, which has potentially serious but largely preventable sequelae in women. Although diagnosis of genital chlamydial infection appears to be declining or at least stable in Australia, possibly due to intervention programs, it remains a relatively common sexually transmitted infection. Comparison of rates and interpretation of the figures is made difficult by changes in screening practices, lack of standard case definitions, denominator information and probable under-reporting. Recommendations proposed for improving data collection for Chlamydia include establishing sentinel sites, standardising the collection of data, and ensuring standard case definitions between sites.