This survey includes discussion on: 1) the physiological and pathological characteristics of the elderly, particularly regarding their reactions to infections; 2) how the required specificity of antimicrobial therapy is achieved in cases of infection; 3) how antimicrobial therapy has affected mortality rates; 4) adverse drug reactions in the aged, 5) general principles of chemotherapy, and 6) the limitations of use for prophylaxis. The guiding principle for the therapeutic use of antibiotics and antibacterials is that the drug should be specific, i.e., chosen on the basis of its effect on the pathogens in susceptibility tests. A close watch should be kept for adverse effects.