Health care personnel must be prepared for the threat of bioterrorism. Our objective is to educate primary care providers, obstetricians in particular, in the prevention, diagnosis, and treatment of smallpox. Smallpox poses a particularly serious threat because of its high case-fatality rate in unvaccinated populations (no one younger than 25 years has been vaccinated, and older persons have little remaining residual immunity). Routine nonemergency smallpox vaccination is restricted to laboratory staff working with smallpox-related viruses. Under these circumstances, contraindications to vaccination are pregnancy, immunodeficiency, exfoliative skin conditions (eczema), and allergy to vaccine components. In case of an intentional release of the smallpox virus, those directly exposed and their close contacts must be vaccinated and isolated. Under such emergency circumstances, pregnant women exposed to the variola virus should be vaccinated because of the lethality of the disease during pregnancy. Currently, there is a limited supply of vaccine available.