The use of newer antibiotics in primary care may substantially increase the cost of antimicrobial therapy, and the additional expense may or may not result in commensurate additional benefit to the patient. This question is considered in respect of older and newer drugs among the beta-lactams, macrolides, and quinolones. The benefits considered are primarily those to the patient, but also those to other parties involved in providing the medication or otherwise concerned with the patient's health. The costs quoted are those for oral forms of the drugs. In addition, other intrinsic and incidental costs to the patient are discussed, as well as the costs arising from inappropriate use of the drugs. It is argued that avoidable use of the newer drugs in primary care may adversely affect antimicrobial therapy in tertiary care by promoting increased prevalence of resistance, and may thus give rise to additional costs to the community at large.