The pharmacological therapy for genital herpes simplex virus (HSV) infection remains dominated by aciclovir, although a number of related compounds are currently under investigation. Recommended treatment for initial genital HSV infection is oral aciclovir 200mg 5 times daily for 5 days, with intravenous therapy reserved for complicated episodes. Although topical aciclovir may be of benefit, no improvement in the systemic symptoms is provided by this formulation. No preparation prevents the onset of recurrent episodes. The management of recurrent episodes is more controversial, with studies of episodic treatment with both topical and oral aciclovir yielding mixed and at times conflicting results. Episodic treatment with oral aciclovir initiated early by the patient appears to have the most favourable results, and if initiated at the onset of prodromal symptoms may abort the episode in some patients. In patients with frequent recurrences, suppressive therapy with oral aciclovir should be considered. A starting dose of 200mg 4 times daily appears to be the most effective, although 400mg twice daily may suffice. The total daily dose should be reduced as far as possible, and treatment should be interrupted on a yearly basis to determine the need for continuing suppression. The management and pharmacological therapy of genital HSV in pregnancy remains controversial and studies of oral aciclovir in late pregnancy are currently under way. Genital HSV infection may be particularly severe in the immunocompromised host and suppressive oral aciclovir should be initiated promptly. HSV resistance to aciclovir is an increasing problem in such patients, in particular those infected with HIV, and may necessitate treatment with intravenous foscarnet.