Objective.To determine how inaccurate communication of patient data by clinicians in telephone calls to the prior-approval antimicrobial stewardship program (ASP) staff affects the incidence of inappropriate antimicrobial recommendations made by ASP practitioners.Design.A retrospective cohort design was used. The accuracy of the patient data communicated was evaluated against patients' medical records to identify predetermined, clinically significant inaccuracies. Inappropriate antimicrobial recommendations were defined having been made if an expert panel unanimously rated the actual recommendations as inappropriate after reviewing vignettes derived from inpatients' medical records.Setting.The setting was an academic medical center with a prior-approval ASP.Patients.All inpatient subjects of ASP prior-approval calls were eligible for inclusion.Results.Of 200 ASP telephone calls, the panel agreed about whether or not antimicrobial recommendations were inappropriate for 163 calls (82%); these 163 calls were then used as the basis for further analyses. After controlling for confbunders, inaccurate communication was found to be associated with inappropriate antimicrobial recommendations (odds ratio [OR], of 2.2; P = .03). In secondary analyses of specific data types, only inaccuracies in microbiological data were associated with the study outcome (OR, 7.5; P = .002). The most common reason panelists gave for rating a recommendation as inappropriate was that antimicrobial therapy was not indicated.Conclusions.Inaccurate communication of patient data, particularly microbiological data, during prior-approval calls is associated with an increased risk of inappropriate antimicrobial recommendations from the ASP. Clinicians and ASP practitioners should work to confirm that critical data has been communicated accurately prior to use of that data in prescribing decisions.