Background: Rates of HIV in New South Wales (NSW) have been stable, but have increased significantly in other Australian states. The reasons for this are unknown and may be associated with differences in the management of sexually transmissible infections (STI) and HIV in different states in Australia. Our aim was to determine if the use of suppressive treatment for genital herpes, the treatment of HIV or STI screening practices were different between states in Australia. Methods: This study was a cross-sectional survey of medical practitioners who are S100 prescribers and members of the Australian Society for HIV Medicine. Results: In general, there were no differences between the clinical practices of practitioners in NSW and other states except that in NSW fewer practitioners tested HIV-positive men who have sex with men (MSM) for syphilis annually (NSW 78% v. others 87%, P = 0.04) or treated MSM with advanced HIV disease (CD4 < 150 × 106 cells L–1) with acicylovir in the absence of herpes simplex virus (HSV) (NSW 4% v. others 13%, P = 0.03), and more practitioners in NSW tested HIV-negative MSM for HSV type-specific serology (NSW 21% v. others 11%, P = 0.02). Conclusions: It is unlikely that the minor differences in HSV and HIV treatment or STI screening practices among practitioners in NSW and other Australian states explains the differences in HIV notifications between these two areas.