Antibiotic dosing is not influenced by age as much as by the weight loss and loss of renal function that occurs with advanced age. The chronic diseases that afflict the frail, elderly person, however, exert a profound influence on the types of infections and the variety of organisms that must be considered in empiric therapy choices. Safety, efficacy, and cost favor the choice of broad-spectrum oral antimicrobials or the newer quinolones for initial treatment of moderately severe, urinary, respiratory, or skin and soft-tissue infections. When parenteral empiric therapy is needed, the third-generation cephalosporins are preferable to multi-drug or narrow-spectrum regimens. To avoid adverse reactions, the frail, elderly patient generally should be given somewhat lower doses at longer dose intervals compared with younger patients.