Although there are as yet no established indications for acyclovir use in pregnancy, the most reasonable uses are for maternal infections such as disseminated herpes simplex, varicella pneumonia, and severe primary genital herpes. Other potential, but more problematic, uses during pregnancy are for uncomplicated primary genital herpes infections, maternal varicella, and for prophylaxis against the recurrence of genital herpes near term. We review each of these potential uses and the pharmacokinetics of acyclovir in pregnancy while emphasizing that at the present time, safety, efficacy, and appropriate dosage of the drug have not been established for any use in pregnancy.