Infectious diseases are common problems. They are different in modes of infection, degree of severity and also treatment. Some infections may resolve spontaneously but some produce morbidity and mortality in the absence of appropriate treatment. In general, successful treatment of infectious diseases is related chiefly to the appropriate use of antimicrobial drugs. However, the best management is prevention before the appearance of disease. This review article presents guidelines for antimicrobial prophylaxis in adults, which includes prophylaxis for human immunodeficiency virus infection, rheumatic fever, meningococcal disease, recurrent uncomplicated urinary tract infection in women, spontaneous bacterial peritonitis in patients with cirrhosis, anthrax, dog and cat bite wounds and tuberculosis.