AIM To assess the benefits and practicalities of setting up a newborn screening (NBS) program in Australia for congenital adrenal hyperplasia (CAH) through a 2 year pilot screening in ACT/NSW and comparing with case surveillance in other states. METHODS The pilot newborn screening occurred between 1/10/95 and 30/9/97 in NSW/ACT. Concurrently, case reporting for all new CAH cases occurred through the Australian Paediatric Surveillance Unit (APSU) across Australia. Details of clinical presentation, re-sampling and laboratory performance were assessed. RESULTS 185,854 newborn infants were screened for CAH in NSW/ACT. Concurrently, 30 cases of CAH were reported to APSU, twelve of which were from NSW/ACT. CAH incidence was 1 in 15 488 (screened population) vs 1 in 18,034 births (unscreened) (difference not significant). Median age of initial notification was day 8 with confirmed diagnosis at 13(5-23) days in the screened population vs 16(7-37) days in the unscreened population (not significant). Of the 5 clinically unsuspected males in the screened population, one had mild salt-wasting by the time of notification, compared with salt-wasting crisis in all 6 males from the unscreened population. 96% of results were reported by day 10. Resampling was requested in 637 (0.4%) and median re-sampling delay was 11(0-28) days with higher resample rates in males (p < 0.0001). The within-laboratory cost per case of clinically unsuspected cases was A$42 717. CONCLUSION There seems good justification for NBS for CAH based on clear prevention of salt-wasting crises and their potential long-term consequences. Also, prospects exist for enhancing screening performance.