In recent years, there have been worldwide efforts to reduce inappropriate antibiotic prescribing. This has mainly been in response to mounting concerns about the emergence of antimicrobial resistance. Surprisingly, there has been little systematic investigation of the impact of antibiotic restrictions on the complications of infection. It is difficult to address this question using randomised clinical trials in light of the often limited numbers of patients that can be included, who are also often atypical of the broad population of patients receiving antibiotic therapy. Observational data from the UK indicate an association between recent reductions in antibiotic prescribing for lower respiratory tract infection in general practice and an increase in pneumonia mortality. These studies suggest a need for further investigations examining the changing patterns of antibiotic prescribing and their effects on patient outcomes in other countries and in other common infectious diseases. Such studies may provide a useful comparison with the changes observed in lower respiratory tract infection in the UK, and could help to improve antibiotic prescribing practices worldwide. It is also important to study whether associated worse outcomes are limited to certain at-risk groups who should be targeted for care.