There is great concern about the extent to which certain microorganisms have become resistant to the antimicrobial agents to which they were once highly susceptible. At the same time, there has been a significant decline in the number of new antimicrobial agents being developed and marketed. This presentation considers the uses and most important characteristics of the new drugs for the treatment of infectious diseases. Where possible, the properties of the new drugs are compared with those of older drugs available for the same uses. A New Drug Comparison Rating (NDCR) is provided for each of the new antimicrobial agents. Selected infections (e.g., HIV/AIDS, malaria) that are of particular importance in parts of the world in which missions programs are based are considered, as are selected infections (e.g., MRSA, Lyme disease) that represent important challenges in the United States.