The purpose of this investigation was to assess the impact of selective reporting of antibiotic susceptibility data on the appropriateness of intended documented antibiotic prescriptions in urinary tract infections (UTIs) among residents training in general practice. We conducted a randomised-controlled case-vignette study in three French universities using a questionnaire with four UTI vignettes. In each university, residents were randomly allocated to two groups: a control group with usual full-length reporting of antibiotic susceptibility data (25 antibiotics) and an intervention group with selective reporting of antibiotic susceptibility data (2 to 4 antibiotics only). 326/611 residents (53 %) participated in the survey, 157/305 (52 %) in the intervention group and 169/306 (55 %) in the control group. For all four UTI scenarios, selective reporting of antibiotic susceptibility data significantly improved the appropriateness of antibiotic prescriptions (absolute increase ranging from 7 to 41 %, depending on the vignette). The variety of antibiotic prescriptions was reduced in the intervention group, and cephalosporins and fluoroquinolones were less often prescribed. Among 325 respondents, 124 (38 %) declared being either not really or not at all at ease with antibiotic susceptibility data, whereas 112/157 (71 %) of the residents in the intervention group declared that selective reporting of antibiotic susceptibility data made their antibiotic choice easier. Selective reporting of antibiotic susceptibility data could be a promising strategy to improve antibiotic use in UTIs, as part of a multi-faceted antibiotic stewardship programme. Microbiology laboratories should be aware that they can have a significant influence on antibiotic use.