Many new antimicrobial agents have become available recently. Several of the new antibiotics may offer an extended spectrum of activity or an improved toxic effect profile. However, they pose such problems as excessive cost and the emergence of drug-resistant organisms as a result of "selection pressure." The majority of common infections can be treated with conventional agents, either singly or in combination. A careful, bedside clinical evaluation, in conjunction with simple laboratory tests, often narrows down microbiologic possibilities and allows simpler antibiotic choices. This results in a cost-conscious approach of using conventional, inexpensive antibiotics in most situations, with new agents being reserved for judiciously selected indications. Such an approach will not only contain health care costs but will also help to preserve the microbiologic ecosystem.