More and more immunocompromised people travel abroad especially in tropical countries where infectious risks are high. Before leaving, these subjects must consult their general practitioner who will determine their fitness in function of type of immunodeficiency, travel destination, availability of medical care at the destination, and possibility of medical evacuation. Counseling should also be provided concerning the precautions necessary to avoid the hazards of exposure to fecal material, venereal disease, insect bites, and sun. Antimalarial drug prophylaxis is the same as for uncompromised subjects. Advising immunocompromised subjects about vaccinations is difficult since there is no consensus on the subject. Administration of inert vaccines is usually recommended but their effectiveness is often diminished and harmful effects have been observed in HIV-infected subjects. Administration of live vaccines is always contraindicated in severely immunocompromised subjects but some live vaccines can be used in moderately immunocompromised subjects. The guidelines for vaccination differ depending on the underlying cause of immunodeficiency: congenital defects, cancer, hemopathy, treatment with immunosuppressors or corticosteroids (transplant patients and patients with systemic disease), HIV-infection, or spleen dysfunction. If there is a high risk of contracting a disease for which vaccination is contraindicated, drug prophylaxis or administration of immunoglobulins can be an alternative. If not, travel should either be postponed or the destination should be changed.