Decisions to use antibiotics require that patient interests are balanced against the public good, that is, control of antibiotic resistance. Patients carry the risks of suboptimal antibiotic treatment and many physicians are reluctant to impose even small avoidable risks on patients. At the same time, antibiotics are overused and antibiotic-resistant microbes are contributing an increasing burden of adverse patient outcomes. It is the criteria that we can use to reject the use of antibiotics that is the focus of this paper. Scanlon's contractualism explains why antibiotics should not be used to gain small benefits, even when the direct costs of antibiotics are low. We know that some individuals now (and probably more in the future will) carry a burden of irretrievable harm as a consequence of treatment- (antibiotic-) resistant infection. If we accept that the dominant justification for use of antibiotics is to prevent irretrievable harm to an individual or contact, then the use of antibiotics for self-limiting conditions, or for the treatment of individuals with conditions for which antibiotics do not substantially impact on outcomes (eg, in the latter stages of terminal illness), or for access based on preference or willingness to pay (internet or over-the-counter access), or the use of antibiotics as animal growth promoters can be rejected. Scanlon's approach also suggests that, with few new antibiotics in the pipeline and an increasing burden of disease attributable to resistant microbes, control of the spread of antibiotic-resistant microbes should be given increasing priority.