Variations in neonatal aciclovir prescribing for suspected herpes simplex virus (HSV) disease are well-known, but there are limited data describing aciclovir prescribing in older children.Medical records of neonates (≤28 days) and children (29 days to 18 years) prescribed intravenous aciclovir for suspected HSV disease (1 January 2019-12 December 2019) in eight Australian and New Zealand hospitals were reviewed. Prescribing indication, HSV testing, aciclovir prescription details, adverse events and discharge diagnosis were recorded.1426 received empirical aciclovir. For neonates (n = 425), the median duration was 1 day (IQR 1-3), 411/425 underwent HSV investigations and 13/425 had HSV disease (two with disseminated encephalitis, four with encephalitis and seven with skin, eye, mouth disease). Of the 1001 children, 906 were immunocompetent. 136/906 suspected of mucocutaneous disease received aciclovir for a median of 2 days (1-2), 121/136 underwent HSV testing, and 69/136 had proven disease. 770/906 received aciclovir for suspected disseminated disease or encephalitis for a median of 1 day (1-2), 556/770 underwent HSV testing, and 5/770 had disseminated disease or encephalitis. Among 95 immunocompromised children, 53/58 with suspected mucocutaneous disease had HSV testing and this was confirmed in 22. Disseminated disease or encephalitis was suspected in 37/95, HSV testing conducted in 23/37 and detected in one. The median aciclovir duration was 3 (2-7) days for immunocompromised children. Nephrotoxicity occurred in 7/1426 and 24/1426 had an extravasation injury.Frequent and often unnecessary intravenous aciclovir prescribing for suspected HSV encephalitis or disseminated disease occurred in children, as evidenced by incomplete HSV investigations and only 5/770 older children having the diagnosis confirmed.